You may already be aware of these resources but ...
- You can find a pre-release version of the Microsoft TFS Quality Center Connector here https://connect.microsoft.com/Downloads/DownloadDetails.aspx?SiteID=628&DownloadID=15667. The corresponding blog post is here http://blogs.msdn.com/jimlamb/archive/2009/01/06/tfs-2008-hp-quality-center-connector-december-pre-release.aspx
- You can also find a commercial bug sync connector here http://www.juvander.fi/TFSQCSync.aspx
- Both of the above resources are references from the TFS Migration and Integration page here http://msdn.microsoft.com/en-us/teamsystem/bb840033.aspx