Keep in mind that TS2010 was never a super, super performer. TS12, with all its bugs is much better at handling graphics. Trainz in general is also performance dependent upon how optimized the content is. Some assets will load and cause even your super workstation, not unlike my bro's machine by the way, to stutter, while other content will load up and run well.
With my GTX780Ti, I am seeing a consistent 60fps running TS12 in windowed mode with some bursts up to 100fps, maybe a bit more, may be a bit less, in non-built up locations.
John