Done a couple of active places but not by accident.
Also done a couple of active/occupied places by accident.
Ironically this active place I did at the start of 2014 was abandoned and demolished a couple of years later - this was a crash test facility where they tested street furniture, lampposts, traffic lights etc against impacts from cars.
Once, whilst trying to find a way into an abandoned aerospace testing facility which bordered an active automotive test facility we took a wrong turn and ended up on their very active test track, once we realised the cock-up we got the hell outta there ha.