I'd be surprised if the signal operates only by schedule (or dispatcher). That would risk triggering the gates etc. based on "ghost" trains but requiring override of some kind for trains that arrive off schedule. Sacramento has what appears to be a loop detector at the stopping point (for a mini-high platform for wheelchair access, at the front door of the light rail train). It also, perhaps, allows for additional coded communication, and in the event of a breakdown of that system there's a manual override in a locked box on the platform. The train signal cannot clear until the the crossing gates are active and fully down. Of course, it may be that the train is still loading/unloading passengers by the time the gates are down, so there may be some delay, but it's usually short.

FWIW, Sac has only recently started ordering Siemens low-floor LRVs to replace some of it's old Siemens U2 cars from when the system started up in the 1980s. They will, of course, have to be equipped to use the same old signals etc. - THAT isn't going to change any time soon. Sac right now is almost a rolling museum line, with 1980s-models Siemens and UTDC (originally San Jose VTA) cars, and some early-2000s CAF cars.