If a commission or other agency or agencies is empowered by another state to regulate and control the amount and character of securities to be issued by any public service company within such other state, then the Commission shall have the power to agree with such other commission or other agency or agencies of such other state on the issuance of stocks or stock certificates or other evidences of interest or ownership, and bonds, notes or other evidences of indebtedness by a public service company owning or operating a public utility both in such state and in this Commonwealth, and shall have the power to approve such issue jointly with such commission or other agency or agencies and to issue a joint certificate of such approval; provided, however, that no such joint approval shall be required in order to express the consent to and approval of such issue by the Commonwealth of Virginia if such issue is separately approved by the Commission.