Agreed. I was just thinking if their justification would be to deter graffiti they would want people to be afraid of being picked up during/right after the act

Agreed. I was just thinking if their justification would be to deter graffiti they would want people to be afraid of being picked up during/right after the act, but I guess it would make sense for them to be worried about someone reviewing the footage later and their picture being passed around to the transit cops.