[danielf]

I would think that a sign 'park at your own risk' is completely void if your car is damaged due to their fault/their equipment. They would have a case if your car is broken into/damaged by a third party, but putting up a sign does not mean they are not responsible for damage caused by their negligence. In the extreme this would mean a company employee could accidentally drive a forklift into your car, and the company would not be accountable. I don't think it works this way.

Obviously, there is a limit to what is negligence (they don't have to stop car thieves/burglars), but seeing it's their fence, I'd think you have a strong case.