I should have been more specific. Although they could use IP geolocation, they can also get data from the cell carrier that delivered the notification to that IP address.
So a gov finds that IP address 7.8.9.0 received one of these notifications at 12:34. They then see that 7.8.9.0 is one of ATT’s addresses. They go to ATT and learn that address was used by their customer onionisafruit at 12:34 and the device was 5ms away from tower A.
So a gov finds that IP address 7.8.9.0 received one of these notifications at 12:34. They then see that 7.8.9.0 is one of ATT’s addresses. They go to ATT and learn that address was used by their customer onionisafruit at 12:34 and the device was 5ms away from tower A.