I'm not an attorney, but in cases such as this, I will always side with the property owner since I believer in Property Rights.
Moreover, I am not a believer in the nanny state courts stepping in to protect those who would fail to read no parking signs and trespass on private property.
And if cars had been towed from this same lot while their owners were attending an Obama rally, I would have the very same view on this matter. I doubt many others here would.
This appears to be a situation where people were deliberately deceived, so their cars would be towed. They should seek justice and compensation through the courts from those who deceived them. Property rights aren’t, and shouldn’t, be an issue.
If the property owner had the cars towed, but wasn’t involved in posting the signs, then he/she’s not at fault and of course shouldn’t pay. The persons who posted or assisted in the posting of signs are at fault.