I knew there were signs posted (only) in the K-Mart parking lot, but my understanding is those were posted with the consent of K-Mart, even if the police did so.
The problem appears to have been how the signs were portrayed to K-mart management, who thought that they would only be applied to non-customers (the signs said "customers only", after all) and that no one would be prosecuted unless they refused to leave.
After initially refusing comment, K-Mart has stated that they did not ask the police to take this kind of action. I have a feeling they feel the same way as the other business that got shafted by the police earlier. I wonder if they will file a complaint of their own (like the other business owner did).
The owners of the Sonic drive-in have grounds for legal action, as they were an unwilling participant who even refused to let the police tow cars left by the people that were arrested. It will be interesting to see if they decide to pursue it or if they decide to let it pass to avoid antagonizing the mob running the local protection racket (i.e. the Houston PD).