Adobe has made some of their OT feature coding available for developers to look at. Thomas (I think) posted a link to the feature source for Bickham Script Pro on Typophile a while back, but the page seems to have gone missing.
It's okay with me if you want to peek at the OT feature code in Proxima Nova (which I know you have). Keep in mind, though, that FontLab does not have access to the source code. The code that is put into the fonts is compiled, so it must decompile it when it opens the font. Because of this, classes will have generic, numbered names and the feature coding will not necessarily make a lot of sense to human eyes. It also may not recompile.