For the past little while, I've been gathering information together about the behavior of TFSDeleteProject. Earlier today, we put the finishing touches on this document, and now it's been published to MSDN. So, if you would like to know all about the behavior of TFSDeleteProject (including how to resolve failures and exactly what data is deleted by TFSDeleteProject), follow this link to find out more.

http://msdn.microsoft.com/en-us/library/dd206696.aspx 

If you have any questions, feel free to post them in the comments section.

 --Aaron