Looks like the public pressure Comcast has been under over its exemption of Xfinity TV traffic from traffic caps has had an effect. Comcast said today that it was suspending enforcement of its cap and trialing a usage-based plan. Of course Comcast says this has nothing to do with the argument currently raging.
Rather than a hard limit of 250Gb per month, Comcast will try out a system where 300Gb per month is included, with each additional 50Gb costing $10. It is not yet clear whether Xfinity TV traffic will count toward usage-based pricing or not, which is the crux of the current dispute. Either way, a usage-based system of this sort has itself proven controversial in the past. But perhaps the market has evolved since then, as certainly it makes more sense than unlimited bandwidth from an economic point of view.
However, according to the engineers at Level 3 in a very detailed blog post today, it does appear that Comcast was doing more than simply counting the bits differently based on QoS tags it was otherwise ignoring. In testing over a congested cable modem connection, Xfinity TV traffic passed through the connection at measurably higher rates than simultaneous Netflix traffic - suggesting quite strongly that Comcast is in fact prioritizing its own traffic. Additionally, there doesn't seem to be a separate channel for the traffic, it all comes from the same pool.
If this is indeed the case, then it seems unlikely that Comcast's opponents in the net neutrality camp will be mollified by the lifting of the caps alone. What's left looks more and more like a fast lane, abeit one that is called a separate, dedicated IP path.