They are indeed. I was somewhat surprised to read that they are (well, at least by Fenner, in the link I provided above) regarded as hardier than CBB's.
The text at
http://www.marinecenter.com/fish/but...nosebutterfly/ seems to indicate that LPS and softies may be at risk, but that SPS should be safe. They make no mention of clams however, which to me is really the big question mark then, because I am envisioning a more or less SPS-only tank for my 280g setup (i.e., no softies, no LPS) but it would most certainly be including my clams.