Houston is one of the last cities to do it that way. Other municipalities and cities put tow truck companies on a rotation. When you get the call from the dispatcher, you better show up in a timely manner or you are off the rotation. Much safer for everyone and drivers don't have to camp out underneath overpasses and such.
Tow truck services are always hated mostly because they are showing up when you are most vulnerable.
"If you run into an ******* in the morning, you ran into an *******. If you run into *******s all day, you're the *******." – Raylan Givens, "Justified."