Glad to hear the study was not done by the AMA. The article you linked to gave that impression initially. (your link to the AMA web site is not working) But I found
another link to a description of the Berkley Study here
I think that there is a lot of interest in lane splitting from motorcyclists elsewhere, but even after decades of the practice in California they still do not have a clear statement as to its being legal. They do not say that it is illegal, so therefore it is
assumed to be a legal practice. But, they also will not come out and say "Yes, it is legal" in so many words. I'm not sure why the ambivalence since it is so widely accepted and praciticed.
If it was legalized in other areas of higher driver "intensity", like I see in most of the northeastern US, drivers would need a huge educational advertising campaign before it would be anything approaching safe to do. A lot of car drivers around here just can't stand to see another car get ahead of them in traffic, never mind one of those social deviant motorcyclists.