[pdkl95]

> Do towers record past telemetry data?

Yes. Did everyone forget about COTRAVELER?

http://apps.washingtonpost.com/g/page/national/how-the-nsa-i...

> the granularity of knowing that a particular tower handled a phone ping is comparatively useless.

No, it's not. A simple correlation with other phones tells you who is traveling together (co-travelers). This only requires knowing which phones are near each tower, at a fairly low temporal granularity.

I'm sure there are additional ways to analyze that data, too. The travel and relationship map that COTRAVELER discovers is merely the project we know about.