Since 4g lots of devices talk on the same freq at the same time and they do math to decode separate logic streams of data - so freq in itself is not enough
I imagine it is distinct enough if you're coned into a specific place. They are probably not looking at the global as a whole but like a radio telescope pointed back at Earth.
I think you're right here. To give a hypothetical from current events, the US/NATO forces may not have direct access to information from Russian cellular networks, but a bunch of cell signals in an unusual place could indicate a troop movement or something.
I have a outdoor air quality sensor that spikes for five minutes each day at certain times. I know each day when my neighbour goes out for a cigarette. On a similar note Strava data once gave away locations of military bases.
If you aren't putting in any effort to obfuscate your data you are not doing enough. There is a reason why our VIPs and anti-censors both do it.
Encryption and other privacy tools alone aren't enough. The IETF and others are putting great effort into encryption but not enough here. Recently Google announced MLS support, hopefully as that is adopted you'll see more effort with Pluggable transports and making it easy to hide data over more than TLS.
