They definitely don't work in 2.6 either. I should have seen some civilians as well, whom I later spotted in the same turn. Just in case the aliens are currently out of camera range. So, there must be some check in the related code for whether we are in a base defense mission.
Some of the cameras seem to be working. I could definitely (well...never say definitely) see an alien via cameras in one turn, and I also could see some alien and civilian corpses via cameras. However, I can't see civilians via cameras (should I ?) - they may be out of "range" but are in line of sight. The camera on the top level doesn't seem to be working.
EDIT
Alien moving around clearly within range of camera on level 8. Should have seen it. Should probably have seen corpse near camera on level 5/4. On level 3/2, can see corpses, works. Also saw an alien in one turn via that camera. Never can see any civilians through the camera on level 1 near the control room, AFAICT they are near and visible from the camera point of view.
So, to summarize, all cameras except the one on the ground level (map level 3/4) don't seem to be working, and confirmed for the one on the top level. The alien spent quite a number of turns there.