I don't have any direct info on t-mobile, but based on my experience with handling backups at an ISP and general familiarity, I suspect the records are still there.
Chances are they aren't on th3 standard service or technical reps screen, which is designed to answer routine customer queries and only goes bck a couple of months, but ...
... but, the call records are needed for long term purposes such as arguing " settlements " (cost sharing) with other telcos, so would be held pretty much forever. Storage space is cheap...
Now t-mobile only "needs" a small subset of the many fields of data generated with each call, so it's possible their archive data doesn't include that code for the cellsite, but getting rid of it, rather than simply storing everything, is more complicated.
I'd suggest the original poster demand (since there's a subpoena involved ...) that t-mobile specify when the record was destroyed, and give a definitve answer about any archives.
Oh, and for good measure ... since we're now hearing publicly about the NSA's telephone surveillance, perhaps he could drop a demand on them and their commercial partners, to find out what they have ...
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