Just like with speeding tickets, if you have a good lawyer it pays, if you dont, you're out of luck. Almost all tow truck company signs say: "Violators will be towed at owners risk and expense". That means you're not just paying for the tow, but taking the risk of them hurting your car, and it's not their fault if they do.
My advice, check out the company and look up any legal documentation you can find about them. And just dont park where you're not supposed to.