Whenever an assessment or reassessment made upon order of the board results in a petition being brought in the superior court or before the board by a taxpayer against a city or town for abatement of the tax so assessed the attorney general in his discretion, upon request of the commissioner, may represent the town or city involved at no cost or expense to the town or city. All costs and expenses of said proceeding, for which the town or city would otherwise be liable, excepting the salaries of the attorney general or his staff member engaged therein, shall be a proper charge against the appropriation for the department of revenue administration. Nothing herein shall be construed as authorizing the attorney general to appear for a town or city in any actions which may be brought against said town or city in tax abatement proceedings other than as specifically authorized hereunder.