Petty crime? Phone Snatching? Sounds like they're trying to downplay the crime of robbery, which is a felony and not a petty crime.
BART will lose riders, whether they release the video or not. Riding these trains during commute times, when trains are crowded with people going to and from work might be safe. But, on weekends and at night, there are just some places you should not go, or things you should not do.
They installed working cameras so they can "solve crimes", but what priority do they place on preventing crime. Not a word was mentioned on prevention and keeping riders safe, just solving crimes now that they have working cameras.
I think this same train system recently took down a phone app that riders could use to report crimes while riding on the trains, for the same reason they're giving for not releasing the video.