You can't do this is any version of Premiere Pro using the multicam feature. A cut will cut both tracks.
What I normally do is cut the video as normal, then I replace the cut audio track with the uncut audio by renesting. Then I do my audio editing in the original sequence on the original clips.
Well, that's another nasty problem with multicam editing in PP. It cuts only the video but not both. The audio track is always that of the first selected clip (of that in the first video track) when I create a multicam sequence. I have manually to open it in the timeline, enable or disable certain audio tracks, go back to the sequence and cut. But when I have to switch the audio for only some camera angles it is impossible, because I can only change the audio track for the whole sequence. Or do I miss something? Maybe it is another cool "design feature"?
You can tell Adobe what you'd like to see, but such improvements will only be available in Premiere Pro CC. CS6 is at a dead end and will not be receiving any more feature updates.