Yes, the IMEI uniquly identifies the phone itself, so if the GSM radio is on, the network can monitor it’s approximate location.
There’s a couple of caveats: IMEI cloning is possible, but unlikely, and he accuracy of the triangulation will depend on a lot of factors including how far apart the towers are and what sort of obstructions there are between you and the towers. My understanding is that it is done by comparing your signal strength at each of the towers as a proxy for distance. If there’s a large obstruction that reduces your signal to a tower it could throw those measurements off. They’ll know you’re in the area, but not exactly where.
Yes, the IMEI uniquly identifies the phone itself, so if the GSM radio is on, the network can monitor it’s approximate location.
There’s a couple of caveats: IMEI cloning is possible, but unlikely, and he accuracy of the triangulation will depend on a lot of factors including how far apart the towers are and what sort of obstructions there are between you and the towers. My understanding is that it is done by comparing your signal strength at each of the towers as a proxy for distance. If there’s a large obstruction that reduces your signal to a tower it could throw those measurements off. They’ll know you’re in the area, but not exactly where.