The taxes imposed by this chapter do not apply to the sale or use of a motor vehicle if the motor vehicle is operated with an exempt license plate issued under § 502.451, Transportation Code, and is for use by:
(1) a public agency; or
(2) a commercial transportation company to provide transportation services under a contract with:
(A) a board of county school trustees or school district board of trustees under § 34.008, Education Code; or
(B) the governing body of an open-enrollment charter school.