"HARD WIRE."
If there is an electric signal, there is a piece of equipment that can pick it up. I remember about fifteen years ago working inside the corporate offices of a major financial institution that Federal laws required computer connections to be shielded. Ordinary wiring could be read from outside the building. Don't know what the state of the art equipment is but I'm sure the spooks have it.
Well, yes, that high end eqipment and more is available to the top levels, but 2000 Joe Schmos driving by with backup cameras in their cars are not going to pick it up.