UP is quite happy to host passenger trains when they are paid what they consider a good rate for trackage rights, and an agency funds capacity improvements they think is necessary to keep the overall velocity of their freight business up. Caltrans pays more for its access than Amtrak does.I'm no fan of UP, and they certainly have done some anti-passenger rail things. But they're not quite the monster that you're making them out to be. And they have done some pro-passenger things too, including their cooperation with Caltrans when it comes to AmtrakCalifornia operations.However, UP has a record of particularly bad behavior, so God knows what sort of trouble they're causing. UP has been causing a lot of trouble with passenger train projects, as far as I can tell just for the sake of causing trouble; being spectacularly uncooperative and deliberately incompetent when dealing with government agencies, in a way which extends well beyond the behavior of CSX or CN, let alone CP, NS, or BNSF. The federal government should buy out UP and get rid of its management, really.
I am not saying that the amount of money in trackage rights and capital improvements that makes UP happy is right, but it is their railroad. But there is no denying the better handling of Caltrans supported trains by UP is largely due to they get more out of hosting them.