But then you realize their north is not the same as physical north, like Montreal, where west/east follows the river instead or real cardinal points.

So if you ask directions in Montreal and someone tells you to go north, it means to go NW. And if you're told to go east, you have to NE. It's easy once in the city because the grid follows that "convention" but you always have to be aware of that detail. We just like to add a layer of complexity.

One quirk of common Montreal parlance is that directions (north, south, east, and west) along the street grid are sharply skewed relative to the actual compass directions. The St. Lawrence River is taken as flowing west to east (even though it flows north or northeast past the island), so that directions along streets parallel to the river are referred to as "west" and "east," and those along streets perpendicular to the river, "north" and "south." In much of Montreal, "north" is actually northwest, and in some areas such as Verdun and Pointe-aux-Trembles it is actually due west.