Yeah, it sounds like they have a deal with MS to put local caches at Comcast data centers and just have those CDNs mirror content instead of every client stream the content on demand.

So this goes over Comcast's super fast DOCSIS network and never over any internet gateways.

Not sure if this is the NN violation others are assuming it is. It seems like a simple "can we put our junk on your LAN to save bandwidth" deal.