Well from the Times this morning and the way Hammonds briefing its suggesting he will find come down mostly on the labour costs of the industry suggesting abolition of things like contractual cross station/down train walking times, 45 minute warm up time, fixed 8 hour shifts replaced with flexible shifts such as 5 or 6 hours which closer match actual train journey times, massive overtime multipliers, etc...
Yes, I was reading those today (I don't know how true any of them are).
The one where the unions apparently threatened to go on strike if an extra carriage was added to the train sounded pretty unjustifiable.
There was another example quoted where a TOC complained that they had to allow a driver twelve minutes to switch end rather than two. I think twelve minutes sounds reasonable as it might be the drivers only chance to have a pee. (I'd post the link but the paper doesn't allow it anymore).
There probably are savings to be made in this area, but they're living in a dreamworld if they think that this will solve all of the railways organisational and financial problems.