Perhaps those were data devices like Hotspots, tablets and the like that can't make calls, thus there is no E911 mandate for said device? IIRC some newer LTE Data devices don't even have GPS, which would make locating a device harder if your a cellular carrier.

> newer LTE Data devices don't even have GPS, which would make locating a device harder if your a cellular carrier.

Nope, AGPS isn’t required. At any given time, multiple cell towers can hear your devices signal. In the rare event it’s just one, you still get a surprisingly accurate location due to a quirk of cell towers (there’s never just one antenna, except for small cells in places like subways, it’s usually three or more using sector panels). Given a 120° direction (or less) and a distance based on time of flight, you usually get within a few blocks in most cities, and that’s without factoring in triangulation or other more advanced localization techniques. One carrier (maybe more) has the ability to localize a person with a range of ten feet (not everywhere, but enough places to turn it into a product they sell), which is generally more accurate than AGPS.

Keep in mind a large part of what a cellular carrier needs to do is know which cell you're in so it can route traffic to your device. While they don't necessarily get device gps access, they literally cannot do what you're paying them for if they cannot locate you down to the nearest cellular base station. (And in most areas, they'll have you connected to enough base stations that they can at least roughly triangular you using signal strength to estimate distance from multiple cells. I don't know if 3G/4G/LTE allows base stations to calculate TOF roundtrip times to get even better distance accuracy like Wi-Fi does, but it wouldn't surprise me if there's not at least something in the spec that can be abused to allow that...)

Was that random phones, or phones you knew were actively in use?

I'd imagine a cellular network has some "exception handling" for devices that are not switched on or in range of any of it's base stations. And I hypothesise that whatever mechanism this is using might not crank up whatever "scan the whole network" behaviour that might occur if a not-currently-geolocated phone gets an incoming call/message? 1/10 seems too high to account for that though...

These were people's personal phones that they had with them, but no guarantee that they were actively being used.