A few days ago, in the San Francisco Bay Area, a group of 40-60 young people swarmed a BART train and platform, robbed and assaulted several people. Watching the news about the event, they didn't show any camera footage, but the BART spokesperson said something to the effect, "We're going to see if cameras were working on board those train cars." There has been no footage released, that I know of, and BART explains the reason for not doing so is that the suspects are minors. I'm not sure how they can tell, with certainty, someone's age between 17 and 18 year of age. Blurring out faces seems to be a standard practice when the age of the people are obviously under 18, but that is not my point.
My point is, this seems like a bad message to send to both the public, and the people doing bad things, that their surveillance system on board trains is questionable. Better public relations dictate that confidence in surveillance systems should be expressed rather than putting in a caveat.