Ariz. Rev. Stat. § 9-500.20
A city or town may provide or assist in providing emergency fire or emergency medical services outside of its corporate limits, if those services are otherwise unavailable or are provided at the request of any law enforcement agency, fire district, fire department or private person, and may receive reimbursement for the costs of providing the emergency services. The person receiving the services, or on whose behalf the services are provided, is liable to the city or town for the costs, and these costs constitute a debt of that person and may be collected by the city or town. In this section the costs of providing emergency fire or medical services are those costs set forth in resolutions adopted by a city or town establishing fee schedules for emergency response, standby charges, fees for fire cause determination or any other fee that may be required or appropriate to provide emergency fire and medical services outside of its corporate limits.
A.R.S. § 9-500.20