Agreed. Even without SP6, Trainz will often use all of my CPU with my GPU chilling under 50% load.I don't know what they are doing to move it from using less CPU to using more GPU.
I would say see if it can be more, like another 10-20%, as the GPU should be doing a lot more work these days.
Give it a thorough testing with that before giving it to the public for testing.
Also, as I have asked before, what are the specs for the systems the developers are using?