In an earlier post, Greyhound Shakedown, Texas Style: I mentioned writing a "concerned rider" letter to Greyhound about a police raid on the bus I was on in Neanderthal County, TX. No reply ever came; it probably went immediately into the wastebin. According to this HuffPo story, Greyhound rolls over for border patrol raids; likely the company wouldn't be any less opposed to small town sheriffs raising revenue by asking its customers to empty their luggage.
The ACLU has been after them about their lack of fight on the border patrol issue, at least.