Most of the laws (as summarized on the page) seem to address only interfering with a person making a call ("it is a crime for batterers to prevent their victims from making a call for help") or interrupting the service (prank calls?). If BART is the one providing the service (or at least the communications medium), it'd be harder to say they are interfering. They simply stopped offering the service. Also, it's pretty rare for an agency like BART to be charged with crimes.

The worst that's likely to happen is someone sues them, but good luck proving damages.