I have not. I did room with a Sax major when I went to college though and his improv classes seemed to also not mesh well with the absolute maelstrom that comes from bringing strangers of different skillsets in from Craigslist. On re-reading what I posted, I don't mean to say that the classically trained as a group can't jam. The ones I met in school couldn't outside of improvisational exercises yet though. Outside of school they make me feel like a child with his grandma's guitar in his hands again.Don't assume.
Ever hear of a guy named Wynton Marsalis?
In my flautist friends defense, he came up with a simple 4 note melody over my groove, but explained that since we didn't have anything defined that he didn't know where he could/wanted to go. I am looking up Wynton Marsalis though, at the moment