After enabling GitHub integrations, you don't see your pull requests on FogBugz cases.
The GitHub button under the Integration menu creates the impression that pull requests should be also displayed.
The GitHub integration is working for pushed commits, but not for pull requests.
Meaning: pull requests appear on the case only after they are merged (committed), but not before they are merged.
We have a registered feature request to have pull requests appear on the cases before they are merged.