> Furthermore, depending on how willing the firmware of your modem is, the signal used to transfer GPS coordinates to the carrier for emergency response situations can also be triggered remotely by carrier hardware.

It should be feasible for an operator to issue a command to the (e)UICC (SIM) in the phone to fetch the current location from the modem and send it back via SMS. At least this was the case for a relatively long time.

Not that it _really_ matters because most people willfully give away their location information to Google anyways. There's a reason why Google has the best Wi-Fi AP -> Location database that they provide commercially. Send them a list of Wi-Fi BSSID's and their associated RSSI's and you'll get a fairly accurate location.

In comparison, using Cell ID's for geolocationing is finicky. In dense urban environments, you're likely looking at ~500 m radius of accuracy - at least based on the commercially available options.