The 29-year-old has been linked with a loan move to the Ligue 1 outfit in recent weeks, having been frozen out at Loftus Road.
Rangers manager Mark Hughes did not even give him a squad number for this season following his red card against Manchester City on the last day of last term, and subsequent 12-match ban.
Barton flew to France on Wednesday and Baup told OM's website: "Joey Barton is in the building. I don't know if it will be finalised on Wednesday or how it will turn out."
Baup had praise for Barton's qualities as a player but warned that if he is to become part of the set-up at the Stade Velodrome then the controversial Liverpudlian must fit into the team ethic.
"He is someone who all the world knows," he said.
"He is an English box-to-box midfielder, he works hard on the pitch and can win the ball back well. He also uses the ball well.
"This is the type of player that allows a team to play at a high tempo and to quickly recover when they lose the ball.
"He has to be part of the project, respect the team rules and work in the greater interest of the team. He must comply with these standards.
"His career indicates that he knows that already. And a player of character is often necessary."