I think you're going to be fighting an uphill battle with this one in regards to copyright. First, I'd imagine you know the difference between a trademark and copyright. Trademark is much easier to identify ownership and prove when someone has ripped you off. Unfortunately, unless you've registered your content, you're going to have difficulty proving that you wrote it (as opposed to possibly ripping it off yourself from a brochure or something...). Above all of that, finding a copyright attorney who is willing to take action on this sort of thing is in itself going to be challenging, let alone expensive and time consuming.
Your best course of action is as you've mentioned. Go after them if their license is suspicious or if you can get them in trouble by any other means. But unfortunately, you're not likely going to get any copyright relief. I had a business outright steal my content, verbatim, and even some of my images. But I couldn't afford an attorney to chase them down and their domain registrar (one of the largest and most widely known) didn't want to do anything about it unless I could prove that I wrote the content and created the images.