§ 19. Exclusiveness of remedy. The benefits provided by this chapter shall be the exclusive remedy of a volunteer ambulance worker, or his spouse, parents, dependents, next of kin, executor or administrator, or anyone otherwise entitled to recover damages, at common law or otherwise, for or on account of an injury to a volunteer ambulance worker in line of duty or death resulting from an injury to a volunteer ambulance worker in line of duty, as against (1) the political subdivision or volunteer ambulance company liable for the payment of such benefits, (2) the political subdivision regularly served by the ambulance company of which the volunteer ambulance worker is a member, whether or not pursuant to a contract for ambulance services, even though any such political subdivision is not liable for the payment of such benefits in the circumstances, and (3) any person or company acting under governmental or statutory authority in furtherance of the duties or activities in relation to which any such injury resulted; provided, however, that the benefits provided by this chapter shall not be the exclusive remedy as against persons who, in the furtherance of the same duties or activities, are not similarly barred from recourse against the volunteer ambulance worker, or his executor or administrator.