"Express" drivers between Dallas and Austin and between Houston and Austin may wear Greyhound uniforms, but they are really employed by the company's cut-rate line, Americanos.
Links:
[1] https://atu1700.org/?q=node/1
[2] https://atu1700.org/sites/atu1700.org/files/take_the_bus_and_leave_the_driving_to...who__eng_span-1.pdf