Ottawa, like many cities, has enacted bylaws to restrict that practice, but there is no way of knowing if that is working or how the short-term rentals are affecting the rental market.

Yup. No way to know. Unknowable. It cannot be known.

Didn't Ricochet do an audit of Airbnb that helped Quebec pass their pretty awesome law?

EDIT: shouldn't the city of Ottawa collect stats on the apartment effectiveness of their new legislation?