I can imagine a world much like ours where it would expected that all such information were expunged when it outlasted its original purpose of directing calls to cell phone customers. Occasionally some systems would cheat but most of those would be found out eventually and suffer opprobrium.
One use of this preserved data is for law enforcement. There are two cases to consider, when the individual was under suspicion when his location is sensed, and when he was not under suspicion. The first case can be handled under a warrant and I think that the second case should be considered an innovation of privacy.
How do we know the phone carriers are playing by the rules? Two ways come to mind:
Technically it is a bit more complex. When I travel to a distant city with my cell phone the cells in that city must inform computers near my home what city I am in so my calls may be routed. The expunging policy must be applied to these information transfers as well.
I dislike legal precedent that refers to ‘expectation of privacy’ since things are changing so fast that expectations have not been formed, and the practice which leads to these expectation may not be what we want. I believe that the ‘wrong expectations’ are being formed today regarding our digital privacy.
If there were laws requiring this data to be destroyed after its ostensible utility, then much of the benefit would accrue even if some companies cheated. The cell phone is the recent obvious example of needless retention of data. There are several other cases and will be many more in the future.
Some have suggested that a cell service provider could adopt this practice at least when their customers were in range of the provider’s cells. This might give them a competitive advantage.