Even if it does have a wifi radio, if you bought your own from someone other than Comcast, you probably aren't part of the Xfinity hotspot system.
> ... you probably aren't part of the Xfinity hotspot system.
Because of the above, I wouldn't be so sure (mostly due to Comcast's reputation).
Personally, when I was forced to use Comcast for a while, I purchased my own "dumb" (i.e., non-WiFi) cable modem. I didn't want to pay their rental fees, I didn't want to run an open hotspot for them, and I already had my own -- much better -- WiFi gear.