Quite often the cable company does not fully kill service to a connection, I have seen many times places where there was not service ordered that still got the basic networks. I think it's actually a law that cable networks have to carry the broadcast networks like NBC/CBS and such, I do not know if the law states that the bare cable has to carry their service without you ordering anything. As above, the signal may stop after a while since they can see if anything is connected to the cable or not (electrical properties change when they read the data) and would kill the connection.