If you think about it, the basic problem Metrolink has been trying to solve over the past 15 years or so is simply a very bad safety record. There have been three bad crashes as a result of grade crossing incidents -- for whatever reason, more than much larger operators like Chicago Metra, NJT, or Metro North have had. (I think the three together have had just one equivalent in the same period, but someone may be able to set me straight. Metra in particular has a lot of grade crossings, but so does NJT.)

Metrolink has had at least two catastrophic accidents due to overrunning signals, again, more than other, much larger operators. This is the one type that PTC would help, although running trains more like Metra or NJT would probably have the same good result.

But even if there's a big BNSF GE at one end of the train, will yet another pickup or SUV at a grade crossing just get squashed like a bug, or will that too cause the cars behind to accordion?

A lot of Metrolink's "fixes" are aimed at PR, very expensive image doctoring.