Without going into detail, speaking as an engineer, one signal... many signals... the distinction is not a serious technical obstacle, other than money, which, again, not a serious obstacle to the state. Do you really believe this type of tech was only used 1:1?
The feds monitor emissions from vans, from aircraft, in vehicles, and from orbit. If they want you, they already have you. I write very high end signal processing software. I assure you this has been going on for decades. We just have better computers now. They have always had the best computers money could buy, so where we are today, they were some time ago.
It's just the way it is.