With the NSA's data mining revealed, the land-line telecoms were outed, but there's still no evidence one way or another that the wireless carriers have been involved. Of course, the customer service reps and PR flacks are issuing denials or refusing to comment, but I'm guessing they were out of the loop.
If the NSA is truly concerned about security and thinks that Total Information Awareness is the way to keep us safe, then leaving out the wireless carriers would lose a great deal of critical data. Many people have only a cell phone, and those people are more likely to be young, transient, and lower-income. Add Muslim to that mix and you've got the demographic profile of a terrorist (and of course, a lot of innocent hard-working Americans prone to harrasment). The London subway bombers even used cellular phones as bomb components to trigger explosive devices, so I'm guessing this is data the NSA really wants.
I see a few possible scenarios. So in the abscence of any real answers, let's just put it to a vote...
Option 1: Don't be so paranoid.
Wireless carriers were excluded from the program. There were too many competing companies and wireless companies pushed back knowing that they'd lose customers if it was discovered. The prepaid market in partcular is fragmented, so it would be hard to keep a program under wraps if negotiations were made with many small carriers.
Option 2: Same as a landline
Either the cell carriers bought in to the program, or some if not all of the call data can be intercepted by the major telecoms anyway. We know that wireless calls to land-line phones were logged, but I don't have any idea -- if I'm on a Verizon phone and call a cingular customer -- what networks does that call pass through?
Option 3: The worst-case scenario.
The wireless carriers weren't involved because they didn't need to be. The NSA has already been intercepting wireless transmissions of various kinds for years, and already had those capabilites from day one. Not only do they log the calls, but can make full recordings if they so choose. Even the prepaid phones bought anonymously or with fraudulent identification are tracked with voiceprint analysis.
I remember hearing a few years ago that digital phone calls were 'impossible' to intercept. I think it was how the information was transmitted (split into packets or something?) but this is the NSA and given their budgets and hardware, who knows what's really possible?