I have heard bad things about how Flock works in particular with respect to tracking people, abuse of police powers, etc. But it was not involved in the event in this article, and it is not the only way of doing mobile phone detection.

My state uses a company called Acusensus, which only captures images for long enough to run the AI over them and then deletes all those without even being seen by a human if no offence is detected, among other privacy safeguards. The humans who do review the ones that AI detects as an offence don't even get to see where or when the alleged offence took place.