2Subject as aforesaid, any such enactment conferring on a local authority any function with respect to the provision, construction or acquisition of, or other dealing with, a sewer or sewage disposal works or any function in connection with drainage shall—
(a)so far as the enactment relates to a main sewer or sewage disposal works primarily serving the sewerage area of the Greater London Council, have effect as if any reference to a local authority were a reference to that Council;
(b)so far as the enactment relates to a sewer primarily serving that area other than a main sewer or to drainage in that area, have effect as if any reference to a local authority were a reference to the council of a London borough or county district, as the case may be:
Provided that this paragraph shall not affect the exercise of any function with respect to a main sewer or sewage disposal works primarily serving that area so long as the sewer or works remains vested in the council of a London borough or county district.