So Shaw Direct has the nice feature of giving you free installation of a new dish at your new address after you move. My question is what happens to the old dish? I don't need it for anything but it just makes me curious. Does it sit at the old place whoever moves in next should they choose to subscribe?

Yes that is correct. The next homeowner or tenant may wish to use it. Besides sometimes removing it can cause damage and would require a tech to come out and remove the dish. It is just cheaper to leave it behind and setup the customer at the new address.