Thanks for the question. Unfortunately, I didn't cover the SAML extension project in the book. Although I was waiting until the very end of the book for some kind of official release in hopes I could write about it, no official release has come out of that project, and I felt that documenting it in the book would essentially be a waste of time, because by the time the official release went out, the API might be different (the hazards of books). Hopefully in the future we will get an official release and I can either add to a 2nd edition, or write up an article.
Hope that answers your question!
Author, Spring Security 3 (the Book), Packt Publishing, 2010