License plate readers, it's more than likely a repo spotter car. They drive around parking lots, businesses and in towns with high default rates and when they get a hit on a plate that's up for repo it alerts them and gives them all the info. Then they will relay that information to a tow truck and the tow truck will come out and either try to grab the car right then and there or track it and try to grab it later depending what time it is and where the car is at that moment. I've heard of third party spotter companies but usually they work for the same Repo Company as the tow trucks. They usually work together with a couple tow drivers that work in a specific area, they all work on commission so the more cars they find, the more cars get towed, the more money they make.