What I meant about Capitol Corridor and Caltrain is that if they can't afford or aren't willing to pay the millions needed for the improvements to run more trains South of San Jose there's no way GGRM could do it by itself.
Also I bet the cost of paying to operate on UP tracks and liability insurance to run those trains on a regular basis would be huge and I assume they would need union conductors assistant conductors and engineers not volunteer crews so even with corporate sponsorships he ticket price might be too high for most people.
Maybe some day UP would relax it's policy on steam engine operations but I doubt it.
GGRM will have it's hands full just trying to overcome the expected NIMBY opposition that Ken mentioned and the logistics of the move from Niles canyon