I think you're going to be on your own. I have tried identifying some of the towing companies on several of the systems, but there's usually not anything that makes them easily identifyable.
On the other hand, Mayor White's SafeClear has given me enough information to identify most of the towing companies with those exclusive contracts, since there are frequently messages about a specific freeway and segment, and "patroling their zone".
What I have captured is in the RR.com database, just take a look at Harris County, and look at all of the LTR systems. If you do identify the talkgroup their on, be sure to update the database so others will know too.