They can and do, but they and the other cell sites can't up and move around. All cell sites have multiple transceivers that are directional. Each site has a unique cell ID and each transceiver has a unique ID. Your phone has GPS. If you drive around, you can find out who doesn't belong. Be careful about publicly disclosing this information.

>Be careful about publicly disclosing this information.

Why, what do I have to fear about that in the United States?

The creator of CryptoCat was targeted by the FBI. Not because he was suspected of committing a crime, just because they didn't like him creating open source encryption software. They actually had Hector Monsegur (Sabu) try to entrap him multiple times to try and come up with some trumped up reason to convict him.

https://nadimkobeissi.tumblr.com/page/29

Moxie Marlinspike can't even fly domestically without jumping through hoops and travelling internationally means they try to seize his electronics and demand the passwords.

I suppose that depends on your tolerance for drama and legal cartooney. One of my former employers and a three letter agency would go after people publicly disclosing such things and the people always backed down. The cooperation between nations can blur the lines depending on what nation you are in. That said, I am not a lawyer so it is probably best to get their input rather than mine.

The disclosure of facts is protected by the First Amendment.

There are sometimes non-legal reasons to be careful.

I dunno if you noticed, but the law doesn't always exactly mean much in terms of what actually happens.

That isn't universally true.

Does that work for DRM encryption keys? I think sony went after a few people who leaked either the blu-ray encryption keys, or the signing keys for one of their consoles.