BC - Mamquam Lake Campground -- Reservations

It may be a municipal campground, based on the suggested price on freecampsites.net
You could try contacting the city/town of Squamish BC to see what they can tell you about it.
Or, maybe the "neighbors" could help. Try contacting the Squamish Valley Rod and Gun Club.
The satellite view of the area doesn't show much detail, but it doesn't look like a well developed campground from the air.