Sorry, but I've been off-grid for a while.
Sean, you make some good points. Thanks for the insight on the foam differences. I don't think that answers the ultimate question though for a couple of reasons.
First, looking at the foams only is an incomplete picture of helmet design, especially in a hockey helmet. Most bike helmets that I've seen are primarily foam, with some sort of THIN shell designed primarily to protect the foam from breaking down. Hockey helmets, on the other hand, have a very thick plastic shell designed to work in conjunction with the foam to distribute trauma. Think of it this way -- bike helmets are like NASCAR cars -- the strength of the structure comes entirely from the FRAME, while the sheet metal surface is strictly for looks; compare that to an airplane which derives much of its strength from the skin. Point is, that the softer foam of a hockey helmet is designed to work in conjuction with the hard shell to distribute force, including blunt, singular force, not just repeated light blows.
Second, certification testing obviously has it's limitations. As evidence of the design for hockey helmets, I offer this common sense proposition -- if hockey helmets weren't designed to ALSO absorb single extreme impacts, the hockey helmet industry would have been shut down years ago from law suits for head injuries. If you don't think that head impacts with the ice or boards occur in hockey at speeds that far exceed most cycling accidents, then you've never played ice hockey.
I think the question of suitability goes back to weight/drag/ventilation -- definitely even 15 years ago, hockey helmet designs ignored these elements. Not today.
Vaughn