I know that some will disagree but I think CS should just pay up for the maintenance/exams required on the mk2/3s, so that the new stock is only introduced on the Highlander once it's properly ready, rather than being driven by the old stock's exam schedule. And if significant problems continue on the lowlander have a mk2/3 set spare to use on that as necessary. I know Serco are already losing loads of money - but that shouldn't be "our" problem - they messed up, either in their projections or in their management of the contracts with CAF. If it's ultimately CAF's fault then they can sort that out between them. Serco is a huge company with no shortage of capital. It's supposed to be one of the benefits of our privatised system that the franchisees take the financial risk. If things go well they profit, if things go wrong, they should bear the cost, not "us" (by "us" I mean both as users of the service and as contributors to the public purse). If Serco are running a massively substandard operation as a result of putting off shelling out for mk2/3 exams then effectively it is "us" who are bearing the cost.
If this would mean that they have to spend an amount of money that's disproportionate to the amount of time the mk2/3s continue in service then that is simply their problem, not ours.
The only other acceptable arrangement would be if they are somehow paying TS some sort of compensation in return for not providing a proper service as per their contract with them. I've not heard any word that anything like this is happening - or is it?
Regarding the comments about being pushed into rushing things by political pressures - perhaps that's part of the picture, but really, again it's Serco's problem. If they were not ready they should have resisted and taken whatever the consequences would have been. If those consequences had been financial penalties - so be it. Their problem. They signed the contract.
There may be complexities to this that I'm not aware of, that mean that what I say above doesn't make sense. Interested to hear what they are if so.