We had an abandoned car in our garage in Toronto once, Dave, me and a bunch of young musician friends I was living with at the time, and that's exactly how we got rid of it too. It had belonged to a crazy artist we knew. He stored it "temporarily" at our place, and "temporarily" became "forever" and it wasn't drivable. So we did what you did, pushed it out on the street and phoned up the authorities. Worked like a charm.