The plan is simply to replicate outbound what is currently done inbound at the ePassport gates - to attempt to match your mugshot as captured by the camera with the photo encoded on your passport chip. So yes, the first thing you will have to do when departing is scan your passport.
I expect mine will work as rarely as it currently does, although a nice Border Force chap at Gare du Nord recently showed me an interesting technique that I'll try in future to improve my chances.
