I checked every one of the bikes on this auction site. There is not one that I would take even if it was free. These are all department store bikes with a litany of potential problems.

Most would be very poor commuters - cheap useless suspension forks, heavy frames and wheels, energy-sapping knobby tires.

To answer your question, the police auction bikes in my city appear to be abandoned or stolen. I assume some good bikes are stolen from time to time, but after looking at hundreds of bikes in these auctions, I don't know why these never make it to the sale floor.

There is basically zero value in attending one of the live auctions, except for amusement. See the auctioneers demonstrate basically no knowledge about the product; if it has full suspension and a bright paint job, then it must worth hundreds! Watch Type A personalities duke it out in the auction for the priviledge of paying more than Wally World retail! Marvel at the incredibly dangerous bikes heading out the door!

If you are willing to hang around a couple of hours in a depressing environment you may get to the bikes that the auctioneers have tagged as 'broken'. This is where the real value is, because what they think as broken usually means that the handlebars have been rotated sideways for shipping, or one of the wheels is loose because the quick release has been flipped.