DB and FS have only collaborated on the project "Here Lies Love". From the Wikipedia for the collaboration, it seems to be an album that was adapted into a musical, and the album features 20 vocalists, and DB and FS weren't participants in the muscal. The Wiki states that there were a couple performances of the album but doesn't specify anything about both of them performing together, and I couldn't find anything else about the performing together either. In the absence of any evidence to the contrary, I think think the act is inevitable.
21/12 - Elton John 31/01 - Fatboy Slim 16/02 - Fire Fight Australia (Queen, Alice Cooper, Daryl Braithwaite, Olivia Newton-John, Peking Duk, etc.) 24/03 - The National (happy birthday to meeeee!) 16/04 - Patti Smith