additional temporary "towers" are sometimes added when very high but transient network loads are anticipated (such as a music festival, or county fair, etc.). not all new towers are sniffers.
If anyone is interested in trying to work around this, I have a few ideas for how to try distinguish a real and fake cell. Temporary event "pop-up" networks should announce valid neighbouring cells.
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.