As cellular carriers roll out better location technologies in the course of their business, the location information sent to law enforcement (as transmitted from the carrier's call database in (near) real time in response to a wiretap order) is becoming more and more precise. The current base station or sector ID paradigm is becoming less important to carriers, and as networks improve, sector data is increasingly being linked to or supplanted by an accurately calculated latitude and longitude of the customer's handsets.
The document ends with a chilling observation:
Cell phone location information is quietly and automatically calculated by the network, without unusual or overt intervention that might be detected by the subject. And the "tracking device" is now a benign object already carried by the target -- his or her own telephone.
None of this is new or suprising, I guess; it's all been covered on "24" for years now. But Professor Blaze puts it clearly and simply, and it's an interesting (and quick) read.