http://www.usatoday.com/story/sports/nfl/steelers/2015/09/11/website-headsets-game-operations-patriots-pittsburgh-new-england-mike-tomlin/72064822/Someone...maybe CW...posted a long blog below on the earlier Patriots cheating. Buried in the middle of that is a reference to the Patriots cutting out the headsets of visiting teams during games, but the person making the statement says it's "small sh-- that happens everywhere".
According to that other article it happens routinely at all stadiums. I guess maybe it's just getting more attention now, but I notice Tomlin says it's always that way at Gillette. The NFL won't touch it, and I don't blame them, but it's clear that it did happen and Belichick is, as usual, FOS.