(1) Where within a period of sixty days, or in cases falling under clause (b) of section 331 within a period of thirty days, after the receipts of any notice under section 333 or section 334 or of the further information, if any, required under section 335 the Commissioner does not refuse to sanction the building or work or upon refusal, does not communicate the refusal to the person who has given the notice, the Commissioner shall be deemed to have accorded sanction to the building or work and the person by whom the notice has been given shall be free to commence and proceed with the building or work in accordance with his intention as expressed in the notice and the documents and plans accompanying the same:
     Provided that if it appears to the Commissioner that the site of the proposed building or work is likely to be affected by any scheme of acquisition of land for any public purpose or by any proposed regular line of a public street or extension, improvement, widening or alteration of any street, the Commissioner may withhold sanction of the building or work for such period not exceeding three months as he deems fit and the period of sixty days or as the case may be, the period of thirty days specified in this sub-section shall be deemed to commence from the date of the expiry of the period for which the sanction has been withheld.
     (2) Where a building or work is sanctioned or is deemed to have been sanctioned by the Commissioner under sub-section (1), the person who has given the notice shall be bound to erect the building or execute the work in accordance with such sanction but not so as to contravene any of the provisions of this Act or any other law or of any bye-law made thereunder.
     (3) If the person or anyone lawfully claiming under him does not commence the erection of the building or the execution of the work within one year of the date on which the building or work is sanctioned or is deemed to have been sanctioned, he shall have to give notice under section 333 or, as the case may, be under section 334 for fresh sanction of the building or the work and the provisions of this section shall apply in relation to such notice as they apply in relation to the original notice.
     (4) Before commencing the erection of a building or execution of a work within the period specified in sub-section (3), the person concerned shall give notice to the Commissioner of the proposed date of the commencement of the erection of the building or the execution of the work:
     Provided that if the commencement does not take place within seven days of the date so notified, the notice shall be deemed not to have been given and a fresh notice shall be necessary in this behalf.