I don't personally know anyone with IBS that's been to a pain management clinic, but I have recommended them to some people on here. A lady I worked with, her husband got agressive prostate cancer and his overall health deteriorated rapidly. One of his doctors (he had a bunch) finally sent him to a pain management center. They were very pleased with it because the pain doctor took over all of his medicines and reduced many of them that were pretty much duplicates (what happens when you see many doctors) and got him on some new stuff that improved the quality of his life. This was not just pain meds, but heart meds, blood pressure meds and a bunch of other stuff. But the very first thing she did when she saw him was tell him to switch his walking cane to the other side of his body. I seem to recall he carried it on his bad side, but when she had him switch, he noticed it was easier to walk immediately; it never occured to him to swap sides.
So I'm thinking that pain management doctors are a lot more than narcotics dispensers. Which, brings me to the part about behavior modfication and psych therapies. I'm not saying a good dose of pain medicine is not warranted, but I've also recommended to people on this board that they see some sort of counselor because, while stress does not CAUSE IBS, it does make it worse. And the more IBS you have, the more you tend to stress about it until it turns into a pretty vicious cycle. A question I have asked before is does a panic attack cause IBS or does getting IBS cause a panic attack? In many people it works both ways. So, if your friend does indeed experience stress from his IBS (is there anyone on here who doesn't???), then learning to control and dissapate the stress can actually be helpful. It in no way means he's imagining the problems or pain, and it doesn't mean he's causing it; it's just a matter of his illness being to the point that it affects his mental health as well. Also, pain doctors may also prescribe yoga or meditation or deep-breathing techniques because they help people get through the pain better (relaxes muscles that start tightening up due to pain), not because they don't believe the pain is real. Kind of like lamaze helps a woman in labor get through her pain. In fact, I would suspect a good doctor would both offer some sort of pain medicine (if not other kinds of medicine as well), AND techniques to help.
In short, your friend should use his good judgment: don't dismiss non-medication suggestions, but at the same time, don't let people tell him that his pain isn't real or that it will just go away if he'd start doing/quit doing X. I suspect that he will get more sympathy from a pain doctor, though, because they should be rather used to seeing people who have chronic pain but no diagnosis as to why.
If you like your pain clinic, then have your friend try them; most people tend to go to doctors and the like based on personal recommendations, and it seems to work out well that way. Also, you know they at least know about abdominal/internal organ pain through you. Your friend shouldn't be a whole lot different.