Our IT operations team put together a whitepaper here Deploying Visual Studio 2005 Team Foundation Server as an Enterprise-Wide Service Technical Case Study that describes how they have rolled out the TFS service offering here at Microsoft.  It describes how one team provides TFS projects to any product group in Microsoft that wants to use it.  It covers the benefits TFS provides to Microsoft, a brief feature set and architectural overview, some organizational insight into how the operations team divides up responsibility and some guidelines we've developed for how we move teams to TFS.

If you are looking at doing something similiar, it's worth a read.

Brian