This is indeed pretty funny, but I think we are missing some details. If, for instance, the reason he ended up backing into his car had something to do with the city's inadequate training of its dump-truck drivers, or if he had been required to turn the truck around in an unsafe space, etc., then I could certainly see a sense in which the city (and it's policies, procedures, training, etc.) would be at least partly responsible. But if it's simply his negligence, then that's different.
But to use my point in a more obvious example, let's say he was just driving by his house with the truck, and some gravel fell out of the truck because there were holes in the tarp or the side of the truck, or because there were chunks of gravel being thrown up by the tires, etc., and his car was damaged by the rocks. In that case it would certainly seem to be the city's fault, and not his negligence.
So I think the merits of this case would depend on just why and how he ended up damaging his car. In some cases, the city would seem to bear some responsibility, in others not.
[Edited 2006-03-16 22:43:56]
Next flight.... who knows.