For the purposes of this chapter, an organized volunteer fire-fighting unit described by Section 615.003(12) is considered an agent of a political subdivision, including a municipality, county, or district, that the unit serves if:
(1) the unit receives any financial aid from the political subdivision for the maintenance, upkeep, or storage of equipment; or
(2) the governing body of the political subdivision designates the unit as an agent of the political subdivision.