Okla. Stat. tit. 63, § 2804

Every system may include police, fire fighting and emergency medical and ambulance services, and may include other emergency services, in the discretion of the affected public agency, such as poison control services, suicide prevention services and emergency management services. The system may incorporate a private ambulance service. In those areas in which a public safety agency of the state provides such emergency services, the system may include such public safety agencies.