The authority to enter into these agreements:
For the City of Winnipeg: The City can require an owner to enter into such an agreement as a condition of issuing a building permit or approving a variance.
See section 240.2(1), The City of Winnipeg Charter
For an authority under The Planning Act: The authority can require an owner to enter into such an agreement as a condition of issuing a building permit or making a variance order.
See section 151.1(1), The Planning Act