Comcast filed a description of its new congestion management system a few days ago. This is what will replace their previous system which throttled P2P traffic. Of course, they backed off that plan a while back, then were told to back off that plan by the FCC, and have appealed that ruling - apparently to give their lawyers something to do. But nevertheless, they have what they call a new 'protocol agnostic' network management system that they will have in place by New Years.
You can go into lots of technical detail, but the basic setup is as follows. If there's no congestion going on, everyone's traffic gets the same priority. If there is congestion and they detect you are using more than they think is too much, then your traffic gets a lower priority. It apparently does not matter what that traffic is - I wonder what happens if one has a heart attack while watching a streaming HD movie, does the e911 voip call that puts you over the speed limit get deprioritized and perhaps dropped? Or do they retain the capability to be protocol agnostic except for e911 calls?
But that's probably too specific a case to deal with just yet. Actually, this congestion management system is rather ordinary and non-controversial - no wonder they didn't hesitate to show it, whereas they didn't want anyone to know anything about the last one. I suppose the real question is: what constitutes congestion, and when should Comcast simply have to add more bandwidth rather than blame its customers? After all, this whole setup is to support the practice of bandwidth oversubscription. They will always sell more potential bandwidth than they can aggregate, banking on the average usage being small relative to the theoretical maximum.
None of this relates to the supposed 250Gb usage limit, it is about rates and not about quantity. You could use only 10Gb for the whole month, but if you did it all in one hour you could be deprioritized. In other words, buying bandwidth from Comcast is like renting a car in Germany - you can go as fast as you want outside the cities on the autobahn but in the city there is a speed limit. And also if you drive too many miles, they charge you extra for that too. But in the case of Comcast, they don't yet give you a speedometer so you can't actually know how fast you are going nor how far you have gone. Hmmm, something missing there I think.