That said, I'm still squeamish about the whole separation between track and train and the way costs/access charges are allocated.
As said elsewhere, subsidy depends on how you look at it (or how your accountants want to look at it!).
I recall sitting with a friend at a station in the London suburbs during the p.m. peak waiting for a train coming out of town - there had been some earlier delay. Whilst waiting, a steady stream of almost empty trains heading, in service, back into town. They pointed this out as an example of waste and why on earth were the railways running needless empty trains (just like a beancounter might if they analysed that particular journey might). It was lost on them, until I pointed it out, that those trains were going into town purely so they can come back out full of people. Regardless of how many people are on it, it needs to get into town!
But short-sighted thinking is a problem endemic in not only the railway industry these days!
An unpleasant side-effect of the fragmented railway is the blaming of everyone else for problems and the open response of "Well, it's not our problem, it's Network Rail's broken signal/ScotRail's broken down train". The passenger, broadly speaking, doesn't care who has caused the problem, they just want it to be resolved - and then the various firms can fight amongst each other after the event.
The thing that has put me off GC/HT when travelling KGX-DON is (apart from 2 hours on a DMU) the problems that you may face during disruption - you're unlikely to find anybody from those firms at either station to help you, and the East Coast staff will not help you as you booked with another firm. I suspect, although I do not know, that the
First CC staff at King's X would try to wash their hands of you even if you are a
First HT passenger.
I'd sooner book with East Coast knowing that, if there is a problem, the next train is 20/30 minutes behind and I can speak to somebody from the firm, at the station, who knows what's what.