Fire Prevention and Investigation - As enacted, authorizes a county that has entered into a written mutual aid agreement with each municipality within the county relating to the provisions of fire services in the context of state military affairs, emergencies, and civil defense law, to fund up to 50 percent of the cost to provide fire services to unincorporated portions of the county using county general funds. - Amends TCA Title 5; Title 6; Title 12; Title 58 and Title 68.