Think it's more to do with LM prioritising their efforts on their own fleet first. If there's going to be a unit miss something due to a lack of parts, it'll be XC's not LM's.
Well, that goes to prove my point; that's hardly a working practice that is going to bring benefits to the passenger overall.
If privatisation hadn't come about we wouldn't have half the new traction that we have, and a lot more half-arsed refurbs. We'd also have a lot more surplus stock, because as a whole nationwide fleet it wouldn't seem so wasteful.
Generally, I'm in favour of the privatisation of BR, but the manner in which it has been done has introduced an awful lot of inefficiencies into the industry that weren't previously present. While privatisation addressed a number of things that were wrong with BR, it has removed a lot of the opportunity for joined up thinking in the rail industry.
Would we really have seen a lot less new trains if the rail network had remained nationalised? BR had a lot of new designs on the drawing board. It remains to be seen how many of those would have got
off the drawing board, but the Networker programme still had a lot of scope for a more extensive roll out, Strathclyde PTE proposed class 157 units (Which I see as the foreunner to the Turbostars) to replace their 156s, and "Intercity 250" was promised for the West Coast main line which would have, hopefully, seen the WCML upgraded for higher speed running sooner than was the case. Not to mention the 1,000 day drought of train orders that surrounded the uncertainty of privatisation.
What we have now is a lot of different new train types, and a lot of different refurbishments to different specs. Half-arsed or not, at least there'd be a standard to train builds and refurbs under nationalisation that is evidently lacking in the privatised railway environment.
Highlighting that having a shared nationwide train fleet would bring economies of scale to fleet sizes acts to point out the inefficiencies of having a large number of separate train fleets, when it would be more efficient to have a single, large fleet.
British Rail had a lot of problems, and was absolutelty woeful in some areas (From what I can work out/vaguely remember, train and infrastructure maintenance practices seemed to be...lacking...when the chips were down). But there's so many holes in the current model of privatisation that even with all the fresh ideas it's brought to the table it's impossible not to pick at them.