Within California, the California Regs apply, known as General Order 95, which are enforced by the CPUC. To make a long story short, the trolley wire height for Caltrain and the spiffy/costly/glizty/sexy HSR is 22.5 Feet. There can be the occasional exception (lower wire), which I think will apply to tunnels 1 through 4. This 22.5 foot height would also apply to the UP's track between SJ and Gilroy (or any other railroad RR track in the state -- excluding certain lighter than rail operations), and as long at it doesn't have to pony up any Uncle Samoleons, it probably won't object.