I didn't realize crews had that kind of flexibility; somehow I had assumed that airline crews were expected to follow SIDs and STARs, when these procedures are available, and that they weren't allowed (or at least weren't supposed to) "roll their own" procedures. I'm glad that they have the freedom to do that. Sometimes it seems like airline crews are drowning in procedures of various flavors. I also think that ATC in simulation might be a bit more gung-ho than the real thing.
I don't know the situation in Europe, although I've been told that European ATC usually assigns SIDs and STARs on the fly, at the time of departure or prior to arrival. I guess pilots have the option of refusing a procedure, as in the U.S.
BTW, I have since verified that the source of the plate is NACO.