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1/ I thought I'd comment on technical details of this story. To begin with, you can test this feature yourself by enabling the "family" location tracking service (so parents can track their kids) with AT&T, T-Mobile, and Sprint.
2/ What you'll find is sometimes the location is exact, such as which booth I'm sitting in at the bar. Sometimes it's a mile away down the street.
3/ There are two types of location information: what AT&T/T-Mobile/Sprint know about you, and what Apple/Google know about you. They are different, and only overlap a little bit.
4/ For all phones, even "feature" phones not running iOS/Android, the cell companies knows which tower you are connected to, the rough angle from the tower, and your rough distance from the tower. It must know these things in order to communicate to the phone.
5/ Depending upon the quality of the signal, this can get you within a few hundred meters. It is logged. When the police request your position information from the cell company, this is the sort of information they get.
6/ When using those "family" services to locate your kid's phone, the mobile company will first try to ask the phone it's location. Your phone will try to figure this out using a number of techniques.
7/ One way is to look at the surrounding cell towers and triangulate ("multilaterate") its position. Phones transmit at minimum power to conserve battery, so towers can't triangulate the phone, but the phone can triangulate itself.
8/ If the phone has a "GPS" chip, it'll also try to use that. However, this is a complicated process that can take 12.5 minutes as it tries to download info from the satellites at 50 bps. That's 50 bps, no 'k', 'm', or 'g' in front of it.
9/ To improve upon this, your phone can download this information over the Internet instead. This gives faster positioning. But more importantly, it can download additional information to improve accuracy sometimes.
10/ When making an emergency call to 9-1-1, the phone company will use the same functionality in order to get the location information and send it to the 911 operator. The government mandates phone companies provide accurate infromation.
11/ The requirements are things like "within 50 meters for 90% of the 9-1-1- calls", or some such thing. Achieving this is hard, which is why phones have so many features to determine location.
12/ Among the features is a "barometer". When that story mentions "even the floor you are on", that probably comes from the built-in barometer, not the GPS. BTW, your fitness apps also use the barometer to track then stairs you climb.
13/ The phone uses GPS, this "assisted" GPS, triangulating with cell towers, barometers, accelerometers, and a few other tricks to get location. Your mobile company like AT&T then can send 4G LTE packets to your phone asking for this information at any time, secretly.
14/ For family plans, they don't allow it to be perfectly secret. They'll send an SMS messages once a month to the phone telling it's owner that the tracking feature is enabled, though they don't notify the phone each time the parent requests the child's location.
15/ For emergency services, you don't need notification, because it's implied. The moment you dial 9-1-1, the mobile company will take heroic efforts to do whatever is possible to find your location.
16/ What's going on in the above story with bounty hunters is that the phone companies are pinging your phone, asking for it's location, without telling you they are doing so.
17/ The reason they do so is that 20 years ago when "location services" were first being added to the phone network, they had grand designs about what features it could provide, such as advertising.
18/ They envisioned the ability to be able to walk by a Starbucks and have your phone ping you and say "would you like some coffee?". They envisioned you being able to ask your phone for the nearest coffee shop.
19/ "But Rob, I can already ask Siri/Google for the nearest coffee shop". Yes, but I'm talking about asking the PHONE COMPANY (AT&T) for this, not asking the Internet for this. Back in the day, they envisioned the phone company controlling this, not the Internet.
20/ Thank Steve Jobs (pbuh) for finally defeating the nonsense that was phone companies, so that you buy a phone from Apple instead of AT&T, and get your services from apps rather than AT&T. The world of mobile phones is divided into two eras: before and after the iPhone.
21/ What Apple/Google/TheInternet knows about your location is different than what the phone companies knows. Your phone runs software to triangulate ("multilaterate") from nearby WiFi access points, getting your location down to inches.
22/ This is down by grabbing the signals from the WiFi chip, uploading it to Apples/Googles servers, consulting their database of billions of WiFi points, figuring out the location, and downloading it back to your phone.
23/ This is usually more accurate than what the phone company knows about you. They can also get the data from the GPS/A-GPS as well, but they often don't know the information triangulated from cell towers.
24/ Anyway, of somebody can tell @josephfcox, I'd love to review the data under NDA so I can match how things work in practice with what I understand mostly only from theory.
