i don't know about the police auctions but I have a friend that owns a car lot and he'd take me to the dealer ownly auctions all the time and there are some really nice looking cars there that got the crap kicked out of them and might not make it another 1k miles before needing major work. Mostly its the big dealers dumping all the crappy buy backs they can't sell.
I'm sure the police auction is totally different. I always wanted to go to one too to get a beatup car. I think if you want a cheap second car you can turn into something you can beat up or a fix me up its a great idea