Riggle nailed it. Ants are everywhere, and I wouldn't try to de-ant a property unless they were clearly causing problems. If I did, I'd make up a solution of sugar and insecticide and set some out at each mound. They feed it to the queen, who lays the eggs for the next generation.
Canada's feds are reasonable about lawn chemicals, and I thought the main provinces with their own restrictions are Quebec and Ontario.
If no solid answer is easily forthcoming, you could talk to the owner about your treating different portions different ways to see what works over time.