Section 15. If land which is subject to a lien for an assessment made under this chapter is subsequently divided by sale, mortgage, partition or otherwise and such division has been duly recorded in the registry of deeds, the board, before the land has been advertised for sale for non-payment of the assessment, may, or upon the written request of the owner or mortgagee of a portion thereof, accompanied by a plan sufficient for the identification of the division of the whole estate, with the names of the different owners thereof, shall, divide said assessment or the amount thereof remaining unpaid, and the costs and interest accrued thereon, among the several parcels into which said land has been divided, assessing upon each parcel the part of the original assessment remaining unpaid proportionate to the special benefit received by such parcel from the improvement. After such assessment has been so divided, only the part of the assessment, interest and costs assessed upon each parcel shall constitute a lien upon such parcel. At least seven days prior to making such division the board shall send by registered mail to all owners of any interest in the land assessed, whose addresses are known to them, a notice of their intention to make such division and of the time appointed therefor, unless such notice has been waived. A person aggrieved by any action of the board under this section shall have the same remedy as a person aggrieved by the refusal of the board to abate an assessment.