Still comes out the borrowing limits though??
Construction wise it does indeed and the HMT all sector infrastructure spend limit is actually the key criteria, which is effectively maxed out for the next 4-5 years hence the HS2 and other project "right shifting" at the moment due to inflation.
So a new government in the future would either have to:
a) increase the limit (More direct government Nuclear new build support for Sizewell C has effective changed the landscape given smaller/zero foreign government support in the future) and/or
b) spread out spending over longer periods (what is currently happening) and/or
c) get local authorities to do more infrastructure works and finance them (TfL, TfGM etc.) and/or
d) PFI or equivalent (accounting rules have change since the last time on this so it is less attractive to government)
In practical terms schemes take along time to plan, design and approve to the spade ready stage hence extra large scheme construction spend has no chance of happening before 2028 (even if there was room below the limit.) Hence the grander NPR scope and HS2 East approval would be about re-election in 2030.
So what could an new Labour government post 2025 get for quicker delivery:
1) existing schemes in the pipeline
i) TRU
ii) MML electrification
iii) final approval of HS2B and the start of a slow spread out construction period (cash flow) to show something is happening
2 NPR scope
i) take forwards existing DfT NRP proposals which will be much more developed over the next 2 years or
ii) start again in places with new bigger scope
3) Bring forwards some quicker to spade ready more local schemes that would be element of NPR (or similar regional brandings elsewhere), again aim for spade in the ground in 2029 before 2030 election, progress could be suitable slow):
eg electrify as follow on schemes to TRU/MML:
Hull
Post MML Sheffield - Moorthrorpe gap
Calder Valley
Significant route upgrade and electrification
Bradford Interchange move etc. and electrify Leeds - Halifax - (Calder Valley)