Couldn't the xbox request program 12983 be sent specific IP and port, while this is via IP I don't think CC(or any other ISP) has ever said ALL their available IP bandwidth will be dedicated to HSI delivery.
The network neutrality "pledge"* only applies to the 250GB's included in your residential package with various prices based on the speed you want to use it.
You might have a better case if you are a biz HSI and TV user where your HSI doesn't currently have a cap (keep pushing, they'll change that) and the ToS is different (not sure biz TV includes ON demand products)
CC and the rest of the industry spent a lot increasing total capacity via D3 upgrades (and other emerging tech), and they don't intend to just give it away.
They will continue to find other services (voice, home security, etc) to pay back and even profit
from that investment, and many of them will be via the "private IP space".