Montreal's need for a physical forward is well-documented, and Frederic's ability to forecheck, create turnovers, and add pressure could give the Canadiens exactly the type of bottom-six presence they're seeking. Adding Frederic to the lineup would likely enhance their team dynamics, providing a tougher presence against their Atlantic Division rivals.
While it may not be ideal for the Bruins to part ways with Frederic, since he is on an expiring contract, they could trade him and he could serve as a rental for the Habs, or wherever else he could land.
If he does end up being traded to a divisional rival, Sweeney would do his best to get all he can out of the Montreal Canadiens.