Tex. Rev. Civ. Stat. art. 4006a

The preceding article shall not apply in cases where the laws of this State provide that such companies as are referred to in said article, or the receivers or lessees thereof, or persons operating the same, or the officers, agents or employés thereof, may grant free passes, franks, privileges, or substitutes for pay to or for the persons, articles or things referred to and mentioned in said laws and said article.