The thread on the UK's inability to do integrated transport has got me thinking. Which bus routes could be sensibly integrated into the current rail network?
The OP asked about which routes could be used - but we seem to be stuck in an argument about the practicalities of co-ordinating things (mainly in Wales), rather than suggestions for suitable routes.
Whilst I appreciate the nostalgia of focussing on routes closed in the 1960s (or focussing on villages/towns with no train station nowadays), I think that two areas worth investigating would be:
a. routes that link towns to the mainline - e.g. in the early Virgin days, there was a (Stagecoach operated) "58" from Macclesfield to Buxton, which provided the town with alternativer links to WCML destinations like Birmingham/ London (compared to travelling via Stockport). Don't just think of places with
no train service at the moment or following historic lines (e.g. Buxton to Matlock) but consider routes unsuitable for heavy rail (where buses can fill the gaps between lines)
b. train lines with only limited service, where a bus service could fill the gaps - e.g. there's only a peak service from Goole to Knottingley/ Leeds, but a bus from Goole to Knottingley could be used to trial demand for an increased train service (connecting at Knottingley with half hourly trains to Leeds), as well as giving people the confidence to plan to use the train if their circumstances change - e.g. if there's only one train a day then I'd have to be pretty confident about finishing work on time to be certain I could rely on the train - similarly, if meetings finished earlier then I might be kicking around Leeds for a couple of hours waiting on that one train - but if there were buses connecting every couple of hours to trains from Leeds to Knottingley then I'd feel a lot happier about taking the train
c. tourist trains (e.g. Midland Mainline used to have an arrangement for a connecting coach to Alton Towers) - there are a lot of tourist places that never had train stations (or where there's no feasible opportunity to re-open one), but you could encourage leisure travel by having a connecting coach for people on days out - it wouldn't even have to be *to* somewhere significant, it could conceivably be a rambling drive through the countryside that comes back to another train station - e.g. from Alnwick station, along the coast round round Bamburgh and back to Alnwick... from Aviemore down the Spey valley towards Keith and back again) - could be a way of encouraging tourists to penetrate places that trains can't serve but which would be a long way on a regular bus service from Newcastle to Bamburgh or Edinburgh/Glasgow to Keith
There are a few places that fit the "a" category round here - e.g. there's a regular bus service from Mansfield to Chesterfield but at the moment Mansfield people are restricted by the Robin Hood line (only hourly north to Worksop, not going south of Nottingham in the other direction) - if you could use the bus to Chesterfield then you could get to Leeds/ Birmingham/ London a lot better than changing at Worksop/ Nottingham. Maybe the express bus from Sunderland to Durham?
In the "b" category, I guess the obvious examples are places like Hellifield - Colne (where there is a railway, but only a Sunday service), but there are some lines with regular services that have intermediate stations with only a token service - it doesn't just need to be about places with *no* trains, it can be about underserved places (e.g. those that could have an increased train service but resources are required elsewhere for most of the day, or there's little scope to stop longer distance trains there (maybe you could run a bus from Morpeth to the villages that only get the token commuter train for Newcastle at the moment?).