Section 12D. Notwithstanding the provisions of any general or special law to the contrary, in any appeal under the provisions of sections 64 or 65 of chapter 59 from the refusal of the assessors to abate a tax or reclassify any real or personal property by an electric company or gas company, both as defined in section 1 of chapter 164, upon motion of any party after an appeal has been filed but before decision is rendered concerning real or personal property of an electric or gas company for any fiscal year certified or following certification for classification by the commissioner under the provisions of section 56 of chapter 40 or any determination of the commissioner made pursuant to section 1A of chapter 58, the board shall properly classify all the taxable property at issue as either real or personal and determine the fair cash value of such property, and the tax that should have been paid, notwithstanding the assessors' original classification of such property or the amount or form of the tax bill received and paid; provided, however, that upon a determination that any property should be reclassified, the taxpayer shall be allowed to file an appeal late concerning the valuation of such property, if an appeal has not been previously filed, within 30 days of such determination and order of the board.

In any determination made under this section, the board shall make subsidiary findings of the proper classification of all taxable property at issue, as either real or personal, the fair cash value and the total taxes that should have been paid for each parcel or item of such property, reduced by abatements, if any, for each fiscal year. Upon such determination, the board shall further find the taxes that were paid or owed for such property at issue as it was originally assessed and taxed, and shall then allocate and credit such taxes as part or all of the taxes that should have been paid for such property as properly classified by it, and such allocation shall be binding on the taxpayer and the assessor and shall be deemed to be the original tax assessed and owed, subject only to any appeal taken pursuant to section 13; provided, however, that if the total amount of taxes that should have been paid under the board's de novo determination under this section is equal to or greater than the amounts actually paid or owed, as determined under this section, the appellant shall not be entitled to an abatement, notwithstanding the local assessor's original tax classification of the taxable property or the form of the original bill received and paid. Upon a determination under this section, the existing official records of the city or town shall be amended and corrected, and assessments and tax bills shall be deemed to have been issued in conformance with the board's determination.