Here’s a post of interest from Siddharth Bhatia in the Visual Studio Team Foundation Server Setup & Administration forum regarding Team Foundation Server support for Office 12:
Office integration features for TFS Beta 3 Refresh are not supported with Office 12 Beta 1.
We've starting looking at Office 12 Beta 1 and TFS and we've found an issue with the PIA support. We're working with the Office team to sort those out. Likely, it will be Office 12 Beta 2 before you'll be able to use Office 12 with TFS.