(1) When the State Government or two or more Planning Authorities are of opinion that the interests of contiguous areas within the jurisdiction of such Planning Authorities can best be served by the making of a joint development plan or a joint town planning scheme, the State Government shall after necessary enquiry constitute a Special Planning Authority as provided in section 40.
(2) Such Special Planning Authority, when duly constituted, shall make a declaration of the intention to make a joint development plan or a joint town planning scheme in respect of the contiguous areas in the manner provided in section 23 or section 60, as the case may be, and thereafter, the Special Planning Authority shall have all the powers and be liable to all the duties of a Planning Authority under this Act and all the foregoing provisions of this Act in respect of the procedure to be followed in preparing, publishing and submitting a development plan, or, as the case may be, a town planning scheme for sanction of the State Government shall apply so far as may be applicable.
(3) The joint development plan or the joint town planning scheme shall specify the parts of the joint development plan or the joint town planning scheme to be executed by the several Planning Authorities in the several contiguous areas, and the several parts of the joint development plan or joint town planning scheme shall, when the joint development plan or the joint town planning scheme is sanctioned by the State Government under section 31 or 86, as the case may be, have effect in the several contiguous areas as if they are separate development plans or town planning schemes :
Provided that, a joint development plan, or a joint town planning scheme may be executed partly or wholly by the two or more Planning Authorities concerned jointly as they may decide in this behalf.