The expression’s new to me. Is it a good-natured acknowledgement of Canadian lack of formality (which has my unqualified affection and admiration), or does it carry an implied sneer? Like most such expressions, I guess that depends on who says it, and under what circumstances. My erstwhile Canadian employer actually swelled with pride when I described his sartorial appearance as “tatterdemalion” (no one else’s dress style calls for a six-syllable word to describe it). His idea of a gesture to formality was to tuck his shirt inside his trousers. Canada is a more civilized country than just about any other, and I think the “Canadian Tuxedo” is a characteristic manifestation of this.
