Mass. Gen. Laws ch. 161A § 29
In the event the directors and any organizations representing employees of the authority have not reached an agreement within 90 days from the date of the expiration of the agreement, either party may notify the other that it desires mediation. The parties may agree upon a person to serve as a mediator or, if unable to agree on said mediator, either party or the parties acting jointly may petition the board of conciliation and arbitration to appoint a mediator from a list of qualified persons maintained by the board.
After a reasonable period of mediation, not to exceed 45 days from the date of appointment, said mediator shall issue a report indicating the results of his services in resolving the impasse. If at the conclusion of mediation the impasse still exists, the mediator shall so certify. In the event, the mediator shall certify in his report the last best offer of each party on each unresolved issue which has been submitted to mediation and shall also certify the agreement of the parties on each issue on which agreement has been reached and shall submit such certifications to the arbitrator selected by the parties. In such event, so long as the mediator shall also certify that the parties have bargained in good faith, either party may notify the other that it desires arbitration of the dispute. Within 10 days of said notice, the parties shall meet to select a single neutral arbitrator. If, within 15 days, the parties fail to select such single arbitrator, either party may forthwith petition the board of conciliation and arbitration to request a list of five arbitrators from the American Arbitration Association and said Association shall certify to the board that such arbitrators on the list it provides possess the qualifications as provided in section 30. The parties shall thereupon meet to select such arbitrator by striking one name each until one name remains and that person shall serve as the neutral arbitrator. If, after 10 days, one of the parties declines to strike their names, the other party shall strike two names and the board shall forthwith select the arbitrator from the remaining three names.
Mass. Gen. Laws ch. 161A, § 29