Why does the LM diesel fleet need replacing?
I'm not saying that it (all) needs replacing and I'm not getting carried away with rumours about what will be in the wining bid of the unknown bidder...
...BUT, there's a number of TOCs that could do with some 150s/ 170s to supplement those that they already operate... the fleet of 172s would be suited to various urban operations (Valley Lines?)...
...and sometimes it's easier to give one TOC a new fleet and use them to cascade compatible stock around other TOCs.
I'm not saying that this *will* happen, but there's some logic in giving LM new toys and then sharing the old ones around may be more efficient than getting GWR/ W&B/ LM/ Northern to all order small fleets of additional DMUs to deal with capacity increases and the lack of committed electrification (plus Pacer withdrawal in Wales).
(you could even come up with a convoluted cascade where LM 170s go to Chiltern to release 165s to GWR.or LM170s to Chiltern to allow loco-haulage to be replaced by six coach DMUs etc etc)
An interesting question is whether there will be any attempt at DOO on LM, at least the WCML services...I suspect not, I think fingers have been royally burnt.
If we are talking about new stock for LM (whether EMU or DMU) then it'll come with future-proof DOO-capabilities which will give the Unions the opportunity to justify a stroke, should they wish.
The fact that the TOC may have no current plans to move to DOO might not be sufficient to stop talk of a strike, since the TOC can't guarantee things beyond the end of their contract.