Section 56. Payments by the commonwealth, or by any agency, authority or political subdivision thereof, pursuant to a contract with any person or entity shall not be made for the costs of any attorney, consultant or other person to advise, consult or provide any other service to such contracting person or entity relative to persuading employees thereof to support or oppose any organization of said employees or any other employee self-organization or concerted activity for mutual aid or protection. This section shall not apply to the costs of attorneys or consultants to assist in collective bargaining with a union or other employee organization recognized as said employees' bargaining agent or to administer a collective bargaining agreement.