You're right. The issue of signage in Quebec in the Charter of the French Language made its way in Canada all the way to the Supreme Court of Canada, which struck down the provisions, at least those that prohibited the use of any language other than French on signage. The Bourassa government of the time decided to use the notwithstanding clause to enable the use of other languages inside the businesses, indoors, as long as French was predominant in comparison to other languages.
Pursuant to that bill, the matter ended up before the Human Rights Committee of the United Nations on the basis of the International Covenant on Civil and Political Rights. It's important here to say that those conclusions of the Human Rights Committee are not binding in law in Canada, but nevertheless, the committee did conclude that the Charter of the French Language, by prohibiting the use of other languages, was contrary to some provisions of the International Covenant on Civil and Political Rights.