(b)where, after the transfer of such property to the transferee but before the date of publication in the Official Gazette of the notice in respect of such property under sub-section (1) of section 269-D, any improvements have been made to the property, whether by way of addition or alteration or in any other manner, the compensation payable in respect of such property under sub-section (1) shall be increased by such amount as the competent authority and the persons entitled to the compensation may agree within fifteen days of the vesting of the property in the Central Government or in default of such agreement as the Court may, on a reference made to it in this behalf by the competent authority or by any person duly authorised for the purpose by the competent authority, determine to be the amount spent for making such improvements.