There is nothing new in the world

I've got a bit of a scrambled up belief system, but the multi-verse as presented by Discworld suits me well. The idea that there is a multi-verse and that anything CAN happen, but not everything DOES happen, because we make the choice between can and does. I believe that there is a place somewhere where all of the ideas and possibilities gather and sleep and give out inspiration to anyone who bothers to listen. And I believe that belief itself can sometimes make the unreal real.

Which is all just prologue to me noticing last night that Night Watch by Terry Pratchett and Life on Mars share several spooky plot similarities, and wouldn't it be fun to have Sam Vimes and Sam Tyler meet up on the beat one night and have a chat?

The Rules of The Internet tell me that this must exist somewhere, because the Internet is the multi-verse personified. So... does anyone know of the existence of such a fic?

(and bonus points if the Brig is involved.)