Heise reports about last years activity of german Authorities. They describe three different ways that authorities can access cellphone related information. Outrage is what often follows this topic. People write about it in a way that seems to be assuming their audience will have visceral reactions. Heise is not the worst here.
It is possible to send a text message / SMS to a cellphone number that will not be displayed on the device. Probably a feature of the SMS protocol that never was intended for use by users in the first place. This allows to gather the location of a phone via cell tower triangulation. In Germany that happens around 100,000 times a year. Likely much less people are affected: It might make sense to track somebody repeatedly.
Authorities also can request all cellphones present in a certain area. If a murder happens it might be interesting to know which cellphones were turned on in proximity. It is not clear if this information also contains triangulation position. In theory it could. This happens less than 100 times a year.
Finally there is the possibility to set up an IMSI device. Also known as a Stingray these hardware device will become a cell tower for phones in their vicinity. All traffic will flow over them. How useful the information is that one can capture is a different question. It does depend on the level of encryption.
I always thought a stingray would make for an interesting Black Mirror episode: An overland bus, housing to a person who the bad people (in fiction there can be these bad people that are just that ‘bad’) want to dispose off. Those bad people have that level of infinite tech prowess that is also only existing in fiction / our imagination. Those bad people ride close to said bus and intercept all traffic from the glowing rectangle in front of the bus passengers. The perps could invent a social media reality that would make their victim the most evil person imaginable. They could, of course, listen in to what is being said on the bus. The very normal bus people would start feeling outrage towards the victim. Who would attempt to defend him (her) self in the ways that we would do it ourselves. But to no avail: The bad people would carefully craft the emotion on the bus. We as the audience would understand why the people so upset. We have been there to an extend ourselves: Looking at a glowing rectangle has made us feel in this way or another before. Feelings lead to action. An angry mob is the most evil thing there is.