Section 29G. Notwithstanding any general or special law to the contrary, the officer having charge of a state agency may retain the services of private persons, companies, associations or corporations for the purpose of recoupment of overcharges to the commonwealth for utility expenses including, but not limited to, electric, gas, water and sewer expenses, under agreements between the operational services division within the executive office for administration and finance and any such private persons, companies, associations or corporations. The state purchasing agent of the operational services division shall, from time to time, enter into agreements with private persons, companies, associations or corporations for the provision of overcharge recoupment services on behalf of state agencies. No such agreement shall be entered into unless proposals for the same have been invited by public notice published in such manner as the state purchasing agent shall direct to ensure the widest possible cost-effective dissemination of the notice, for at least 2 consecutive weeks prior to the time specified for the opening of said proposals. All such proposals shall be opened in public. Said state purchasing agent may reject any and all proposals. Any such agreements shall provide, in the discretion of said state purchasing agent, the manner in which compensation for such services shall be paid. Under regulations established by said state purchasing agent, such compensation may be deducted and retained from the recoupment of overcharges or paid by the commonwealth from existing expenditure accounts without additional appropriation therefrom; provided, further, that said state purchasing agent shall allow access to such agreements by political subdivisions of the commonwealth, including but not limited to towns, cities, counties, local housing authorities and any other instrumentalities. Said state purchasing agent shall report to the comptroller annually a list of all private persons, companies, associations or corporations with whom said state purchasing agent has agreements for recoupment of overcharges during the fiscal year, and the amount of overcharges recouped and the compensation paid to each such person, company, association, or corporation. Said comptroller shall include and disclose this information as part of the annual report under section 12 of chapter 7A.