My local buses used to have something on the screens that would occasionally get stuck in a reboot loop between something that looked a bit like BIOS text and then MS-DOS. This was over a decade ago though. The screens were designed to switch between different views from the bus's various cameras. I think the idea was to discourage anti-social behaviour by reminding people they were being watched.
But I guess the contract ended and things proved too expensive or too hard to maintain because the next batch of buses didn't have screens in them. The cameras didn't go anywhere though.
