Brennan is alleged to have entered a seating area during Toulouse's 28-13 European Cup victory over Ulster last month and punched a supporter, who has since begun criminal and civil proceedings.
Representatives of the Toulouse forward requested an adjournment of the hearing on the grounds the outcome could prejudice the criminal proceedings in France and affect Brennan's right to silence.
But the decision to proceed with the final hearing ensures the 33-year-old, who is facing a lengthy ban, will discover next month if his playing career has been ended prematurely.
Before the incident took place, he had indicated his decision to retire at the end of the current season.
Earlier on Monday, it was confirmed Brennan had been banned by the French Rugby Federation until March 15 - the day before his hearing will take place.
The International Rugby Board requested Toulouse take the measure as it was "in the interests of the game".
Brennan is alleged to have struck Patrick Bamford, leaving the 25-year-old accountant requiring medical treatment at the ground and on his return home to London.
Brennan claimed he was provoked by derogatory chants during the game.
Bamford is also taking libel action against a number of news organisations which reported the incident.