Mass. Gen. Laws ch. 31 § 39A
Any fire service personnel subject to the retraining requirements of section 39 shall be classified as a conditional employee during the retraining period as a precondition of reinstatement to his position. For purposes of this section, "conditional employee" shall mean a permanent employee of a fire department separated from his position because of disability for a period of time of more than 5 years. Such employee shall be entitled to the continuation of his disability status with no other compensation of rights due him until such time as he has successfully completed any approved retraining program required pursuant to said section 39 and has been subsequently reinstated to his position. No such employee shall increase his average rate of pay for pension purposes prior to the successful completion of the retraining program and reinstatement to his position. Such an employee shall be regarded as a member of the department from which he was separated to accommodate any retraining program approved by the personnel administrator.
Mass. Gen. Laws ch. 31, § 39A