71. Whenever the Government sanctions a plan of a proposed public street or open space, it shall announce the fact by notification, and the publication of such notification shall be conclusive evidence that the plan has been duly made and sanctioned; and the proposed public street or open space to which such notification refers shall be deemed to be a projected public street or open space, and shall be so deemed until- (a) such street or open space has been declared, under section 66, to be a public street or open space, or (b) the said notification has been cancelled: Provided that such cancellation shall not affect the validity of any action taken by the Kartripakkha in pursuance of the said notification.