I can't answer your question because splatter from local WGN here in the Chicago area usually blows out CKAC in these parts. (Although with a little patience and a good null, CKAC is definitely do-able).
Perhaps, however, I can offer a couple of clues. First of all, Patrick Hernandez is of Spanish-Austrian-Italian heritage, but a native of France. Although his major hit was sung in English, it's certainly not unusual to hear him on a French language station.
More significantly, it's very common to hear music in English on French stations....just as true for Paris as it is in Montreal. In fact, anywhere you go in Europe, a high percentage of what you'll hear on local music stations is likely to be in English. Several years ago I was in the Birkenstock outlet store outside of Bonn, Germany. Local radio was piped in, and everything I heard was American. The lone exception was "Nikita"....by Elton John! The jock and the commercials were German, but the music was in English.
I've also spent a lot of time listening to "The Arrow", a classic rock a.m. station (675khz IIRC) out of Amsterdam which has a decent signal 24/7 in London and in parts of several other countries. This station has (or I think more correctly "had") a large international audience with music in English being the common denominator. Almost all of the music in English, but jocks and commercials all Dutch.
And finally, I don't know how accurate my observation is, but IME, Canadian talk stations tend to be more inclined than their U.S. counterparts to flip to (automated) music overnights.
So my guess is CKAC is what was heard.