FWIW, we hit 256gb, and we got a call, threatening if we passed it again in 6 months we would be banned from Comcast for 12 months. (Someone in the house accidentally left a torrent sending for 3 weeks)
Perhaps whether they call you after the limit depends on why you went over the limit. It should be easy to determine if the reason you went over is a torrent (even if they can't figure out what torrent), video streaming, or something else.