24Vac supply may remove interference. This is often due to there design isolating a ground loop from via the PSU.
Similar effect to isolating a ground loop via "humbug" loop isolation on the signal cable, just on the power side.
You didn't mention much else about the installation either, UTP or coax, power supply locations, camera types and transmission type, any tests etc.
Tearing like in your OP would always make me think ground loop, hence my post.