I think the fact remains, that they are permitted in Harris County (rotation system or contract system -they've always been permitted in CS) but they are not necessarily being called by HCSO Dispatch. They are actively listening for crashes to respond to. When in the area, they can then be summoned. It isn't the same as anything that's been done in BCS because it allowed wreckers to get repetitive jobs instead of rotating through. They are heavily regulated just like BCS. No one ever said they could break laws to respond to a crash.
Here is the county ordinance for Harris. This is only for unincorporated areas.
https://www.harriscountyso.org/Documents/Services/Harris%20County%20Tow%20Truck%20Ordinance%208-10-21.pdfFor inside Houston, they have an ordinance for contract wreckers. Once again, it appears they are numerous, and respond on request (listening and getting close - 100ft per ordinance). There are also certain parameters for freeways that are different than simple city streets.
Here is the city ordinance for Houston.
https://www.houstontx.gov/police/general_orders/600/600-10%20Towing.pdfBoth BCS, Harris County, and Houston are heavily regulated when it comes to law enforcement/crash tows; however, knowing specifics of ins/outs for BCS, I know that BCS wreckers are not scanning to respond to a crash. They're being directly summoned by a Dispatcher if they aren't called by an involved party. In Harris/Houston, they're listening and getting there on their own to wait for their "call".