That's a tough question, and I doubt you'll get a good answer to it. But, hops and cocao are two different types of bitterness in my opinion. I typically never adjust hop levels when I add it to my boils. Just think of it as the bitterness you'd taste from biting into a 100% chocolate bar.
I'll have to talk to the head brewer at the brewery I work for and see if he knows about the difference in alpha acids. I believe chocolate has AA's, but it's a different type. I'm no expert on the chemistry side of brewing, so hopefully he can help.