I am not sure if it is still like this, but with TWC used to work across the city with the same Cable Modem (MAC address?). For whatever reason I had moved my cable modem to a different part of the city and it worked just fine. Not that they couldn't look at the routing path, but that may be limited to knowing you are on this street/building, but I am sure almost every has their cable modem at the place on the bill.

It is not you on the plan the TSA cares to keep safe. It is what the plane can crash into. Since planes fly over state borders it affects interstate commerce. Oh, and we loose our rights.