Notice what you said - suspected terrorists to track. I would be in favor of an expedited process to provide records for a phone number and the next level of phones called from that phone. And it could be provided quickly.
But that is far different from mining the call data to look for calling patterns.
I'd need to know more about the mining part. Are they just mining the data for patterns willy-nilly, or are they assembling a warehouse of data to be mined once a starting point is provided? You can't assume that it's just a phone number and one generation from that. You have to look at all the calls to the number, all the calls from the number, all the calls to and from those called numbers, etc, until the paths reach an end. Then you have to look at time of day, durations of those calls, names of the accountholders, were they businesses, what kind, etc.
Actual mining for intelligence (beyond tracing a particular number) would go like this: once you had a specific profile of a terrorist cell (like what I described in the prior paragraph), you would then analyze all the other numbers to see if they exhibited the same profiles, such as is there a cluster of calls to a pivotal number, where one or more of the numbers called a hardware store, another called a gun shop, and the calls were under 2 minutes in duration and occured at night?
By comparison, in the financial world, for example, you would use data mining to analze who were your platinum card holders, then you would analyze the transaction history of your platinum card holders to see what they looked like 5-10 years ago, then you would look for green card holders today who matched what platinum card holders looked like 10 years ago, assume they would become platinum card holders and target them for marketing.
That's data mining.
-PJ