Re-identification is a very different risk than the one considered by the UC Santa Barbara researchers in Wang, Gang, et al. "Whispers in the Dark: Analysis of an Anonymous Social Network." (2014).
According the Washington Post and other outlets, they do have approximate location data: "So the NSA is collecting information about my location as well as who I’ve called? It appears so. Cellphones make calls using the closest tower. So if the NSA knows you made a call using a specific tower, they can safely assume you were near that tower at the time of the call."
Re-identification is a very different risk than the one considered by the UC Santa Barbara researchers in Wang, Gang, et al. "Whispers in the Dark: Analysis of an Anonymous Social Network." (2014).