What cameras are you using? and where are they located?
I think your installer has ran the video wire along side of a "charged" wire....
I've found that most cheaper cameras have very little protection for this.... It could also come from the video source wire...
For an example, I have this camera mounted about a foot from the electric motor in my golf cart... It use to be worse, but I've since used some 3M alloy tape to help from the electric radiated stuff...blah..blah...
Watch when I apply throttle in reverse... are these the lines you're seeing?
http://www.dawgbonez.com/Videos/dawgbon ... 20Cart.wmv