I think "cannot" can easily mean that they are not permitted to according to their internal policies and procedures, even if they might have the technical abili

I think "cannot" can easily mean that they are not permitted to according to their internal policies and procedures, even if they might have the technical ability to do so. "Listen to" is something a human being does, requires a warrant. "Record/capture" is something that a computer does, does not require a warrant. This would be consistent with what parties inside and outside the government have been saying. Until now, no government rep has yet said that calls are not being recorded; they are simply saying that they are not being listened to. The fact is, being able to get a warrant to listen to a recording that you made two years ago of someone, before they were under suspicion, is a very different thing than being able to get a warrant to begin recording and listening to someone. I think the government would assert that the former is equally permitted under the fourth amendment as the latter, although I would bet that most Americans would disagree.