I am certainly not an expert on cell tower data, but I do wonder: how much can it change over time when cell tower data is something very specific and explicit that LE can acquire fairly easily when investigating a crime? From my basic understanding, what is acquired from triangulating cell tower data is different than, for example, tracking that is enabled by location based services on third party apps. This technology has certainly improved significantly in just the last few years. Location based services on phones and third party apps are more precise, if turned on, than cell tower data, but it's a different thing entirely.
Still not extremely recent, but here's this:
A quote from the linked article: “We should remember: data is created to help deliver telecom services, not to control citizens or for surveillance,” Willer said. He conceded it could be valuable to police, but insisted its primary purpose was to facilitate communication between users.