Most CCTV cameras produce analog composite video because it's easy to carry along normal co-ax cables. The frame rate is 16.6 or 20mS, the same as 60Hz and 50Hz so the strobing risk is high. Bear in mind there are two methods of exposure control, one uses a mechanical iris driven from a small motor, the other adjusts the CCD capture time. The iris method has the advantage of better depth of field in bright light conditions and the capture method has the advantage of being purely electrical and hence cheaper. Given that you are talking about times when street lighting is operating and it is therefore fairly dark, the longer capture time in some cameras may average out the flicker to some extent.
Brian.