I'm sure there are circumstances where a warrant might get issued for that data. More telling is the implication from his statement that the data exists and is being maintained.
The phone system HAS to keep track of where your phone is, in order to be able to route incoming calls to the right cell tower. His statement implies that the information is logged, and the logs are archived. Somewhere, there is a file that contains where your cell phone has been, all through the days and weeks.
Good, because I'm beginning to suspect that my cell phone has been cheating on me.