Presumably they are legal, otherwise whoever built the bus wouldn't have done it.
I wouldn't be too sure about that. I once got a ticket on a three year old semi trailer for a "missing" light. Now, I
have no idea whether the officer or the manufacturer was right, didn't bother to look up the law, just paid the ticket.
The officer said I needed some lights on the front of the trailer, visible from the front. It doesn't matter that you can't see
the front of the trailer from the front when hooked to a tractor. Maybe he was just lonely, it was 2AM in St George,UT, he probably
hadn't seen anyone through his scale in a few hours.
I've found that it doesn't really matter what the law actually says, the rule is whatever the officer says it is. For the most part, they know
that someone from 2000 miles away is generally just going to pay the harassment tickets.
I've also seen lots of things on RV's that aren't legal.