I am not sure whether it is! It is certainly not to a UTM coordinate system.
Using the geographic coordinate, one gets to 22e Av in Montreal. In Google Earth, changing to UTM coordinates, one gets (approximately) 610000e, 5046670n in zone 18T.
Your drawing gives coordinates for the same spot as 297600e, 5047360n (approximately).
So I reckon that Montreal has its own mapping grid. You should enquire at the city map makers if they have a conversion.