I believe it was my 2010 article that was the first to highlight law enforcement obtaining cell site dumps:

http://www.cnet.com/news/feds-push-for-tracking-cell-phones/ "When the FBI was stymied by a band of armed robbers known as the "Scarecrow Bandits" that had robbed more than 20 Texas banks, it came up with a novel method of locating the thieves. FBI agents obtained logs from mobile phone companies corresponding to what their cellular towers had recorded at the time of a dozen different bank robberies in the Dallas area. The voluminous records showed that two phones had made calls around the time of all 12 heists..."

I'd be surprised if the FBI didn't do the same thing today, as a very bare minimum.