In a pair of unreleased memos seen in the usual spy-shot fashion, Sprint and T-Mobile both have, at least internally, discussed the Carrier IQ saga with their employees.
The memos discuss the use of Carrier IQ as you'd expect -- as a metrics tool for improving network and device service, and both reiterate that Carrier IQ isn't being used to spy on text messages, phone calls and the like, backing up responses that Carrier IQ recently gave The Verge in an interview.
T-Mobile: "T-Mobile does not use the tool to obtain the content of text, email or voice messages, or the specific destinations of customers' Internet activity. It is not used for marketing purposes. T-Mobile uses the Carrier IQ diagnostic tool to gather device data for effective troubleshooting and to increse the overall device and network performance for our customers.
Sprint: "Sprint uses the Carrier IQ data to only understand device performance on our network so we can identify when issues are occuring. ... Even with Carrier IQ, Sprint does not and cannot look at or record contents of messages, photos, videos, etc., nor do we sell or provide a direct feed of Carrier IQ data to anyone outside Sprint.
T-Mobile also details which of its current phones have Carrier IQ installed. You'll want to read the entire memos, which you can find at the source links below.