Section six of the [41 & 42 Vict. c. 76.] Telegraph Act, 1878 (which empowers the Postmaster-General to establish telegraphic lines on certain undertakings) shall apply to underground air-raid shelters, premises and parking places, and works connected therewith, constructed by a local authority under Part II of this Act, as it applies to the undertakings mentioned in the said section six, and section seven of the said Act (which makes provision as to work done in the execution of certain undertakings which involves alteration in telegraphic lines) shall apply to any work authorised or required to be done under this Act as it applies to work done in the execution of such an undertaking as is mentioned in the said section seven.