Your information is out of date.  The law was changed in 1993 so that it no longer conflicts with the Charter, so the Notwithstanding provision was not needed.

"On December 21, 1988, after the decision of the Supreme Court of Canada in Ford v. Quebec (A.G.), the National Assembly of Quebec employed Section 33 and the equivalent Section 52 of the Quebec Charter of Human Rights and Freedoms in their Bill 178. This allowed Quebec to continue to restrict the posting of certain commercial signs in languages other than French. In 1993, after the law was criticized by the United Nations Human Rights Committee, the Bourassa government had the National Assembly rewrite the law to conform to the Charter, and the notwithstanding clause was removed."

https://en.wikipedia.org/wiki/Section_33_of_the_Canadian_Charter_of_Rights_and_Freedoms