This is not only California, but world wide. Matter-of-fact, in many jurisdictions it's much worse, as there nation-state organizations (such as the Chinese intelligence apparatus) have much better access to cell phone carriers.
Underlying this is a very difficult and troubling question: what is public and what is private? The radio waves emitted by a cell phone are pretty much by definition public. Anyone can relatively simply build a radio receiver which detects a cell phone's transmissions (without decoding the encrypted traffic, like voice or data). But there is enough information there to (a) know that a cell phone is present, (b) it's location with reasonable accuracy, and (c) being able distinguish different ones. That is exactly equivalent to me sitting at my front window, looking out at the public road, and seeing people walk by on the sidewalk: I can tell that there is a human walking by, I can tell where they are, and I can distinguish Alfred E. Neuman from Don Martin, just by their looks. And there is nothing preventing me from sharing that data: I can post of Facebook everytime I see Alfred or Don.
Where it gets troubling is this: Now imagine a town where every person sits at their front window, and continuously posts updates of where Alfred and Don are seen. Or say that the police department installs cameras at every street corner, tracking who is walking around where, and storing that (the faces of Alfred and Don are quite easily recognized, so it doesn't take much effort). Given that any private citizen can see Alfred and Don in public, and given that they have a free speech right to talk about that and remember it, why do we think that the police need to be prohibited from doing something that normal people can do? And if that logic seems to apply to optically recognizing faces (with cameras), why does it not extend to doing the same with cell phones and radio receivers?
In the US, a lot of this circles around the 4th amendment, prohibiting "unreasonable search and seizure". Is it a search if a cell phone app or radio receiver sees something that is in the public sphere anyway? Is it unreasonable that various law enforcement agencies (whether local police or intelligence) band together, to get efficiency of scale by bulk purchasing data from efficient commercial vendors?
But even if my hypothetical arguments above sound reasonable: This inexorably leads to a surveillance state. How do we prevent this? Should we poke out the eyes of any person who looks out of their front window? No. Do we need to hamstring the ability of law enforcement to fight crime? That's insane.
Let me tell you a little story. About 4 weeks ago, an ambulance and fire truck came to our neighborhood. All they knew was that a medical monitoring device (one of those high-tech wrist watches) had reported a person falling. The location was inaccurate by about 1/2 km, so they looked at the wrong place, and didn't find any fall victim. The phone number of the person who had fallen was unknown, for reasons of privacy protection. They left again, having been unable to locate the accident victim. About 3 hours later, the wife (looking for her husband when he was late for dinner) found him dead, near their house. In this particular case, it isn't clear that knowing location and identity accurately and quickly would have helped save his life; his injuries may have been too severe anyway. But this (extremely sad) story demonstrates that privacy has a real-world cost. Emergency response and law enforcement exist for a good reason, and they save lives and prevent crime. Finding a compromise between making them efficient and effective, and preventing a 1984-style totalitarian state is difficult. Undifferentiated anger doesn't make it any easier.