It's not clear from the article exactly what BART did. But they never used the word "jam" or anything else to imply deliberate interference.

Now, if they simply turned off their cell repeaters, that is within the letter of the law (ie FCC R&R) as I understand it. I don't agree with either the action or their self-serving justification reasoning for this stupid asinine bone-headed unsafe unwise decision, but it's not a violation of the laws.

OTOH, if they are jamming cell phone frequencies, nuke the bastards.