The Westminster Government IS in control of the Rail Network in England and Wales, The Scotrail franchise is let by the Scottish Parliament, and the Wales franchisee is awarded by the Welsh Assembly.... whatever makes You think it isn't?
The level of Services are set by the DoT,
The purchase of Trains has to be approved by the DoT,
The FRANCHISES are let by the Dot, there is more 10x money pumped into the Railways now than under BR.
So called PRIVATE COMPANIES get huge subsidies.

It's just an excuse to pretend that the railways are not in government hands.