TxDOT used low band for all communications in most parts of the state. A few places like El Paso had high band repeaters back in the 70's even before the DPS moved to high band.
When I lived in El Paso over 30 years ago I seem to remember an equal amount of traffic on low band and high band. Back then all I ever found was the 151.055 repeater and two low band channels. 47.18 was channel 1 and had the most traffic. 47.06 was channel 2 and was the statweide base-to-base frequency.
Around 10-15 years ago they started putting high band dual mode P25 repeaters everywhere. Some or maybe all of them are IP networked. They built a bunch of new 180' self supporting towers in many places. Around that time they started letting low band licenses expire or cancelling them. Most of the trucks in the Fort Worth and Wichita Falls districts had the low band antennas removed a few years after the high band repeaters were installed but the towers still have low band antennas. I don't know if there is any low band left.