Just as AT&T, Sprint, manufacturers, and Carrier IQ itself have done, T-Mobile has now responded to a request for information from US Senator Al Franken on how it makes use of Carrier IQ's many performance logging capabilities. The overall message in T-Mobile's letter is a similar line that we've heard elsewhere: that T-Mobile collects "technical data solely to understand what is happening on the device and the network so that [it] can more effectively and directly troubleshoot issues." The company also points out that it doesn't see the contents of text messages, email photos, videos, or voicemails, and it doesn't log keystrokes; furthermore, its use falls within T-Mobile's privacy policies and it requires Carrier IQ (which stores the collected diagnostic data in its own servers) to adhere to the same terms.

Also notable is that T-Mobile just began installing Carrier IQ's services in May of this year, and at this point, only nine devices have it installed: HTC's Amaze 4G, Samsung's Galaxy S II and Exhibit II 4G, LG's myTouch, myTouch Q, and DoublePlay, and three newer BlackBerry models. In total, "approximately" 450,000 customers are using those nine, and there's no indication that it intends to slow or halt its use of the service. Now that it's better understood, there may not be a compelling reason why carriers should consider doing that anyway — but if nothing else, an explicit "opt-out" capability would seem like a wise move for everyone involved.