Assuming that HS2 actually gets built as currently proposed, I would be surprised if many of those reading this forum live to see HS2 get to Scotland. Trains using the southern parts of HS2 will be extended north via WCML & ECML, probably calling only at Preston before Glasgow & Edinburgh (WCML), and calling only at Newcastle & Edinburgh (ECML).
Intermediate stations are likely to remain served by conventional WCML and ECML trains, running to revised (possibly slower) timetables, and requiring passengers to change at somewhere like Preston or Leeds if they wish to use HS2 to get to/from London.
The SNP will probably whinge a lot, but unless Scotland is willing to fund most of the building & operating costs, there is unlikely to be a business case to extend the current HS2 proposals.
Darlington will be a calling point on the ECML. The recently signed Tees Valley unitary authority devolution agreement has a condition included, that stipulates, that Darlington station must be made HS2 ready.
I'm not sure how this will effect the original aim of having a Tees Valley interchange as proposed in the early HS2 documents.
The indicative service pattern in the HS2 Business Case for the ECML was for 4tph to go north of Leeds.
These were as follows:
1tph Newcastle, Darlington, OOC, Euston
1tph Newcastle, York, OOC, Euston
1tph York, Toton, OOC, Euston
1tph Newcastle, Durham, Darlington, York, Meadowhall, Toton, Birmingham
That looks like a not too unreasonable a service pattern although I suspect there would be a couple of changes to that once the politics gets involved namely:
- Demand for a direct Durham - Euston service.
- Demand for a direct Northallerton - Euston service.
- Demand for a direct Euston service from stations north of Newcastle (especially Alnmouth / Berwick).
- Demand for an Edinburgh - Toton service.
You can kill all these birds with one stone by extending the York terminator to Edinburgh calling at Northallerton, Durham, Newcastle, Alnmouth, Berwick.
The calls could be 1tp2h at Northallerton / Durham, Alnmouth / Berwick.