Which doesn't come close to filling the capacity of the route.
The only way HS2 could get even close to filling its capacity was to propose an enormous country spanning system that would take over essentially all long distance services.
That's not necessarily a bad thing, however, as I suggested on the 390 turbo thread, HS2 services could connect well with TPE 390 (i.e. replacing their 397's between Manchester or Liverpool and Scotland) services to provide better journey times for TPE but also giving faster London - Glasgow than direct with HS2 services (however the HS2 services to Scotland would be retained so people have the choice of speed or direct) which would give a higher frequency of advertised service.
It would also shift some of the "local" travel away from the HS2 services which would mitigate the slightly lower capacity of their trains.
However back on the main topic of the thread, there's also been suggestions in the past that XC could shift to Moor Street, which is it happened would mean that there'll be another reason to improve the interchange experience/time between HS2/Moor Street and New Street.
However, for those who wish to interchange to local services, distant it's worth noting that Moor Street gives a different selection of stains, so for those heading to those stations they benefit from HS2 serving a station closer to Moor Street.
Also, if the walk time is a barrier (and many will debate how much time it is, but for some that will be fine for others it's not), they have the option to use the classic services. Now whilst these will have a few extra stops in, which might slow the services down a bit, it does give them the option.
Now assuming that the number of Avanti services serving Birmingham New Street is limiting the ability to run further local services, the question which could be useful is, does the service pattern suggested potentially reduce the number of these longer distance services so other services could be run? (I don't know, which is why I'm asking).
However if XC moved there would be. Therefore, if there's a more frequent local service that could aid with journey times.
Also, whilst much is said about the increase in transfer time, currently at New Street, the journey time planners typically say that there's a 15 minute change time when changing from Avanti to get a service to University. This means that even allowing 12 minutes walk between platforms it would still be possible with that current gap (and so the extra walk time wouldn't impact on the journey time savings from HS2).
Before anyone says, but the HS2 services would be arriving earlier, well currently we don't know the timetable. However given that there's probably more scope to pick when the HS2 services arrive at Birmingham (due to having to interact with fewer services to get there) there's a fair chance the times could be fairly optimal.
Even if there was a 30 minute change time at Birmingham, given that HS2 is reducing journey times by 29 minutes, by the time you add in the minimum 15 minute current change time for the services through University the net saving is still 14 minutes for that line.
The same is true if services through Tipton (15 minutes change time currently).
Whilst services through Witton have a current change of 12 minutes, that would still be 12 minutes faster with a 30 minute change time.
The big winner would be services through Gravelly Hill, which currently have a 20 minute change time, so increasing that to 30 minutes from HS2 services would mean a 19 minute journey time saving.
Based on the above, it would require more than a 44 minute change time to increase the overall journey time. For example, let's say it's just about possible to change in 15 minutes and so the timetable is optimised for that for services through Tipton, for those who are unable to make that perfect (15 minute) change they would see their journey time increase by a full 1 minute if they then caught the next train.
A lot of the discussion to date that I'd seen hadn't considered the current change times, which is why I'd thought that it was worth looking at this.
Basically, unless I've missed something, I'm struggling to see how any of this would actually make things worse in terms of journey times. Granted, in theory the current interchange times could be reduced, but it's likely that they couldn't be changed by much.