Notwithstanding chapter 7 of Title 28 or any other general or special law or any charter or local ordinance to the contrary, new collective bargaining agreements, and any amendments, to new or existing collective bargaining agreements, (collectively, “collective bargaining agreements”) entered into by the city, town, or fire district or the school department, shall be subject to the approval of the fiscal overseer, budget commission, or receiver if the fiscal overseer, budget commission, or receiver is in effect at the time. No collective bargaining agreement shall be approved under this section unless the fiscal overseer, budget commission, or receiver has participated in the negotiation of the collective bargaining agreement and provides written certification to the director of revenue that after an evaluation of all pertinent financial information reasonably available, the city’s, town’s, or fire district’s financial resources and revenues are, and will continue to be, adequate to support such collective bargaining agreement without a detrimental impact on the provision of municipal or fire district services. A decision, by the fiscal overseer, budget commission, or receiver, to disapprove of a collective bargaining agreement under this section shall be made in a report to the parties; provided, however, that the report shall specify the disapproved portions of the agreement and the supporting reasons for the disapproval. This section shall not be construed to authorize a fiscal overseer, a budget commission, or a receiver under this chapter to reject or alter any existing collective bargaining agreement, unless by agreement, during the term of such collective bargaining agreement.