I have the Signature Double Play, which has Sports & News, but not the Big Ten Network. I added the Sports Entertainment Package which gives me the BTN, I believe, as I have it. I can't look at/manage my packages as when I try I get the error 'it looks like you have Netflix, call 800-XFINITY'. When I do look at my local channel lineup, when logged in to MyXfinity.com, it shows BTN SD and BTN HD channels. It depends on your location as to whether it is available in your market. I am in the Northeast, northern Vermont zip code 05478. You should call 800-XFINITY to find your answer.
I think Big 10 Network is available on the Sports & Entertainment package (usually an extra $10/month) outside of states with Big 10 teams in them, where it would be on one of the "regular" tiers of service.