My current understanding of the glyphs includes the idea that whatever it was originally contined many ligatures, possibly even a cursive script. Some of these properties shine through in the current form, which on the surface looks like majuscule. For example, I believe cc might have originally been a cr ligature. So it's cursive presented as non cursive. That is why I don't believe in one to one substitution, and it is also why I am afraid statistical analyses wont be able to tell us the full story.
Edit: the reason why I tell this now is because it might explain complementary distributions based on surrounding glyphs
Edit: the reason why I tell this now is because it might explain complementary distributions based on surrounding glyphs