“Area of operation,” in the case of a county authority includes all of the county except the area within the territorial boundaries of any city for which an authority has been authorized to transact business. Except as authorized by Section 34312.5, a county authority shall not operate in any city located in the county and in which an authority has not been authorized to transact business unless the consent of the city governing body has been obtained. If an authority of a city within a county becomes empowered to transact business and exercise its powers, a county authority empowered to transact business and exercise its powers has no power to initiate any further project or leased housing within the territorial boundaries of the city, except as provided in Section 34312.5.