I have seen that stated but I do not agree with it. The pot of gold on which HS2 depends is only available because the politicians are determined on doing it. It could equally well be made available for other projects instead if the politicians could make those other projects a focus of equal determination. I am also concerned that it will lead to other projects failing to get off the ground with politicians saying "we're already spending £enormous on the railways, we can't spare any more". It is a great shame that the major parties are all pro-HS2 so that it cannot be a matter to affect how people vote in the forthcoming election.
What project isn't being taken forward as a result of spending on HS2?
I don't agree with the points made in favour of HS2. The economic argument is something I will not comment on myself because I consider that all economics comes from fairyland and we'd be better off if it went back there, so I shall say only that large and respected institutions which don't think economics comes from fairyland do consider HS2 unsound and leave it to them to argue that aspect for me. Why the government, which does believe in economics, is so ready to dismiss them is beyond me, but it does seem to be a general failing of government that once they get a bee in their bonnet about some daft scheme or other no amount of argument even on their own terms will dislodge it.
Passenger numbers are growing year-on-year at a faster rate than the government had ever predicted. If this continues - which looks likely given the factors involved - there won't be space left for passengers or freight on the railway. When you start running out of space, you start limiting economic growth. If you don't build HS2, and leave the classic network to struggle, you're going to incur an economic cost. It's not 'free' not to do anything.
Britain is too small and dense for the journey time reductions to be really significant - especially from Birmingham. And quoting the reductions by themselves is misleading because it fails to take account of the fiddling on at either end - getting to the origin station and getting from the destination station to where you actually want to go - which can already be comparable with the time spent on the main leg even with current schedules. It is the same fallacy that we have already seen applied to conventional rail only on a larger scale. To further speed up those parts of a journey which are already fast may be simple and may make for good headlines but it is very much a case of diminishing returns, and the real gains come from the less glamorous and more difficult task of making the slow parts less slow.
Birmingham is too close to London for it to be significant, but that's why HS2 isn't just a railway between London and Birmingham. The business case relies upon it being used for services running further north, and it just so happens that it makes economic sense to split it into two phases in the West Midlands. The original 2010 HS2 plans specified the London-West Midlands route in great detail but all the economic justification still relied upon the expectation that it would continue to Manchester and Leeds.
Journey time savings of 50% to Manchester and Leeds, and in future 50% to Scotland once the full captive line is built, are not to be sniffed at. These are precisely the sorts of journeys which the speed improvements of HSR make much better - London to Manchester will now be around an hour, which would make it possible to properly split a working day between the two cities. London to Scotland would be only two-and-a-bit hours, which would mean a business day trip would be feasible in a way it currently isn't when it's 4 hours 30.
That less glamorous work is happening right here, right now, all across the network. However, there is only so much that can be done without the need for major works. If you look at the scale of individual interventions you can see they're starting to get bigger and bigger - take a look at the plans for the Norton Bridge flyover and you'll see 6km of brand new railway being built. Any similar interventions will need to be the same scale or larger, because all of the smaller, easier ones have already been done to get us to the state we're in at the moment. The MML is being electrified and upgraded for 200km/h running in places, the ECML is being resignalled all the way from King's Cross to Doncaster, the various important lines around the North of England and in the Central Belt of Scotland are being electrified, the GWML is being completely modernised, the Chiltern Line is seeing the Evergreen projects, the list goes on and on.
The argument that "Europe has high speed rail therefore we ought to have it too" and that it is "embarrassing" that we don't is so dumb as to be unworthy of comment. I find it embarrassing to have a government that uses Muuum, Jean and Johann have great big train sets, why can't I have one too? as a basis of policy.
No, that's not what HS2 is being justified on.
The capacity argument is fallacious. HS2 cannot significantly release capacity on conventional lines because it only serves the endpoints. It can only replace trains which go between London and Birmingham/Manchester/Leeds non-stop. Correct me if I'm wrong, but I don't think there are any, or very very few. All the trains which call at intermediate stations have to be retained otherwise the service to, from and between those intermediate stations goes down the tubes.
No, what it means is that the large number of people who do go on these trains from end to end, despite them stopping during the journey, would then switch to HS2 so that they wouldn't take up any space on the remaining classic services which would still be used by people who live in between. Also, when you're not having to appeal to end-to-end travellers, you don't need to run as fast by skipping as many stops as possible, so more people would be able to use the train. With that, you can then fit more trains on the classic lines since they'll have more regular stopping patterns. If you actually look at the things HS2 Ltd have produced you'll see proposed stopping patterns for the WCML, MML and ECML once HS2 Phases 1 and 2 have been implemented have actually been produced. The only remaining long distance WCML services would be one to Chester/North Wales, one to Scotland via Manchester and Stoke, another to Scotland via Birmingham and one more Birmingham service, all of which would stop at most major WCML stations like Milton Keynes and Rugby.
If a new line on that route or similar is to be built it would be better to build one for freight. This avoids the difficulty of needing to call at lots of intermediate points to be any use because it is already well established that rail freight works best for long-distance haulage between a few major hubs, and it releases capacity for real by not only reducing the number of trains needing to use existing lines, but by removing a whole class of trains with their own acceleration/speed/braking characteristics which makes the business of organising paths for the remaining classes that much simpler.
Freight services run non-stop, so their normal running speed is approximately their average speed, which is what matters over long distances. Even though passenger services may run at faster speeds, their average speeds will be lower since they will stop regularly. As a result, freight and stopping passenger services can actually fit together not too badly. The trains which cause problems are the non-stop ones which run at full linespeed, e.g. the current Scotland services which run non-stop to Warrington Bank Quay or York. These are the ones you put on HS2.
Rather than spend money improving service between London and four towns which already have excellent services - and at the expense of reducing the service available to other towns if the purported capacity improvements are to materialise - I would prefer to see it spent on sorting out things which the current railway network does notably badly. Journeys in directions to or from London are something it does pretty well. Journeys at right angles to that tend to be somewhere between painfully slow and tedious and not worth trying. Many of the routes which used to run at right angles to London no longer exist and those which do remain tend to have a ropy service. If we are going to spend huge amounts of money on the railways I would far rather see it spent on reopening these closed routes and upgrading the existing ones so that the railway becomes a truly useful means of making journeys at right angles to London.
It's not a case of one or the other. The east-west rail link is happening now, as is the improvements being made to TransPennine services. The case for these is improved by HS2, since they become more useful as more north-south services can stop where the east-west lines cross.
It is galling to see such worthwhile projects as East West Rail getting stuck in the mire on the eastern section because a few miles of new construction are needed, while the hundreds of miles of new construction for HS2 don't seem to be a problem. Bedford to Cambridge is one of those journeys which you just don't do by train - the alternatives being either all the way into London and all the way out again, or all the way round via Leicester, Peterborough and Ely, both of which are ridiculous. Uckfield-Lewes - which should never have been closed, and wouldn't have been had it not been for East Sussex County Council pulling strings behind the scenes to save themselves a few quid on bridging it - is another one whose possible reopening is dragged out endlessly over problems which are very minor compared to HS2. A third example is taking ten years to get moving on the Halton Curve, which should be a no-brainer - not being able to run direct trains between Lime Street and the North Wales coast for the sake of a mere ten million pounds to fettle up something that already exists is really silly.
So we shouldn't build HS2 because we're not solving other problems first?
Another area where the money could be better spent is on providing longer trains - by far the simplest way to increase capacity, on any line, not just the West Coast, and also making journeys much more pleasant for passengers. Nobody likes being crammed in like sardines. Voyagers are widely criticised for being far too small, and now the mistake is being repeated with 5-car IEP sets apparently to replace full-size HSTs.
5-car IEP sets which are intended to be coupled up when they leave King's Cross or Paddington, so that they may split to serve different destinations well enough without providing too much capacity.
Virgin run 11-car Pendolinos. How are you going to extend them further? The new IEP sets will be either 234m long or 260m long (2x5 car). How are you going to extend these further, once a 10th car is added to the 9-car sets? London Midland run 12-car 350s in the peak. How are you going to extend these further?
I could go on but I've probably said enough

There are many, many deficiencies of the current railway network the remedying of which would be a far better way to spend the money than on HS2, and it could be so spent if the political will to do it was there.
DfT's 2007
Delivering a Sustainable Railway stated
"Higher speed is not the only or best way of cutting journey times. Nor is it without cost. Increasing the maximum speed of a train from 200 km/h to 350 km/h means a 90 per cent increase in energy consumption. In exchange, it cuts station-to-station journey time by less than 25 per cent and door-to-door journey-time by even less."
I don't see how a ~50% journey time saving (2 hour 8 minutes down to 1 hour 8 minutes for Manchester trains) is less than 25%.
The same DfT that produced this report, back when Labour thought the future of the railways was bio-diesel, now strongly advocates HS2. If you think their current support is unreasonable and that their opinions are biased, then why would it be unreasonable to say that their previous opposition was biased against the idea?
Please describe how you're going to cut journey times between London and Manchester, without using high speed rail. There's only so much you can do to improve things at either end.
As you say, the capacity argument is fallacious. Because of the very limited number of places it would serve, HS2 could not replace long distance fast trains on existing tracks.
You can think this all you like but you're just as wrong as someone saying that the law of gravity does not apply to them. Just because you may not want it to be true, doesn't mean it isn't true.