Did anyone else notice the scene where Paul calls home and asks if John is there, John is using a Motorola Dyna-TAC 8000 cellphone (more commonly known as the "Brick Phone).
Now if his mother is using a regular phone, why is John using a cell phone, didn't the prop department have any real cordless phones to use.
"All opinions are well reasoned and thought out, any similarity to reality is pure coincidence."
The Feds have invaded the home and installed all manner of surveillance gear by that point. I just always went under the working theory that it was tied into some local repeater that the feds were using.
It's not like the military guys were worried about bending a few FCC rules - however to allow an unencrypted rebroadcast wouldn't make a lot of sense compared to just patching in another land line phone, so it may have been done to look high tech - just like the DeLorean sitting out in front of somebody's garage as the semi trailers with all of the lab gear / raw materials arrived.