Because it is probable that the pattern and detail of the machinery for mutual aid among 2 or more jurisdictions may differ from that among the party jurisdictions of this compact, this compact contains elements of a broad base common to all party jurisdictions, and nothing in this compact precludes any party jurisdiction from entering into supplementary agreements with another party jurisdiction or affects any other agreements already in force between party jurisdictions. Supplementary agreements may include, but are not limited to, provisions for evacuation and reception of injured and other persons and the exchange of medical, fire, public utility, reconnaissance, welfare, transportation and communications personnel, equipment and supplies. [PL 1999, c. 696, §1 (NEW).]