§ 122. Contracts between railroad companies and bus companies owned by former; approval of commissioner. Whenever the commissioner has made an order authorizing any street railroad company or railroad company to substitute the operation of stages, buses or motor vehicles in place of cars or trains upon tracks on any portion of the route of such railroad, and such company is the owner of all of the capital stock of a bus company, such street railroad company or railroad company and such bus company may, subject to the approval of the commissioner, contract for the use of their respective routes, or any part thereof, upon which stages, buses or motor vehicles may be operated, and such routes shall thereafter be used in such manner and for such time as may be prescribed in such contract.