Section 85H1/2. Notwithstanding the provisions of section eighty-five H or any other general or special law to the contrary, in any city, town or fire district which accepts the provisions of this section and in which there are no permanent members of a police or fire department, as the case may be, the selectmen of such town or the prudential committee of such fire district may retire from active service any call firefighter or any member of a volunteer fire company or reserve, special or intermittent police officer who becomes permanently mentally or physically disabled by injuries sustained, through no fault of his own, during the actual performance of duty as such firefighter or police officer. A person so retired shall receive an annual pension equal to two-thirds of the average annual salary of a first-year, regular, firefighter or police officer in the local area; such average to be determined by a survey of three surrounding towns, as determined by the public employee retirement administration commission. Whenever a call firefighter or member of a volunteer fire company in a town whose service as such had been approved by the prudential committee of the fire district or by the board of selectmen of such town, or a reserve, special or intermittent police officer of a town or a reserve police officer or reserve or call firefighter of a city is disabled because of injury or incapacity sustained in the performance of duty, through no fault of his own, and is thereby unable to perform the usual duties of his occupation at the time such injury or incapacity was incurred, such police officer or firefighter shall receive from the city or town, for the period of such injury or incapacity, a minimum annual allowance equal to the average annual salary of a first-year, regular firefighter or police officer in the local area, such average to be determined by a survey of three surrounding towns, as determined by the public employee retirement administration commission; provided, however, that no such compensation shall be payable for any period after such police officer or firefighter has been retired or pensioned or for any period after a physician designated by the board or officer authorized to appoint police officers or firefighters in such city or town determines that such incapacity no longer exists.