Another option can be just seeding a few phones around the area and have them report moving (or transient) towers.
Something like this maybe? https://f-droid.org/en/packages/info.zamojski.soft.towercoll...
Why, what do I have to fear about that in the United States?
Your baseband (radio) might expose neighbour cell data - iPhone field test menu shows the announced neighbour data.
Hypothesis is that a rogue tower will not have valid neighbour cells announced. They could try listen in for valid ones and advertise those.
A lot of the ways to detect will depend on the generation of network being spoofed - 4G networks will also advertise signalling for legacy 2G and 3G circuit switched networks. Rogue sites might not.
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.