Try learning the law for yourself, rather than getting someone else's interpretation of it. So, as the states law say, here are the definitions of an "Authorized Emergency Vehicle":
TRANSPORTATION CODE
TITLE 7. VEHICLES AND TRAFFIC
SUBCHAPTER C. VEHICLES, RAIL TRANSPORTATION, AND EQUIPMENT
Sec. 541.201. VEHICLES. In this subtitle:
(1) "Authorized emergency vehicle" means:
(A) a fire department or police vehicle;
(B) a public or private ambulance operated by a person who has been issued a license by the Department of State Health Services;
(C) an emergency medical services vehicle:
(i) authorized under an emergency medical services provider license issued by the Department of State Health Services under Chapter 773, Health and Safety Code; and
(ii) operating under a contract with an emergency services district that requires the emergency medical services provider to respond to emergency calls with the vehicle;
(D) a municipal department or public service corporation emergency vehicle that has been designated or authorized by the governing body of a municipality;
(E) a county-owned or county-leased emergency management vehicle that has been designated or authorized by the commissioners court;
(F) a vehicle that has been designated by the department under Section 546.0065;
(G) a private vehicle of a volunteer firefighter or a certified emergency medical services employee or volunteer when responding to a fire alarm or medical emergency;
(H) an industrial emergency response vehicle, including an industrial ambulance, when responding to an emergency, but only if the vehicle is operated in compliance with criteria in effect September 1, 1989, and established by the predecessor of the Texas Industrial Emergency Services Board of the State Firemen's and Fire Marshals' Association of Texas;
(I) a vehicle of a blood bank or tissue bank, accredited or approved under the laws of this state or the United States, when making emergency deliveries of blood, drugs, medicines, or organs;
(J) a vehicle used for law enforcement purposes that is owned or leased by a federal governmental entity; or
(K) a private vehicle of an employee or volunteer of a county emergency management division in a county with a population of more than 46,500 and less than 48,000 that is designated as an authorized emergency vehicle by the commissioners court of that county.
(Continued)...