Nope. "interchangeability" -- mean that you can remove an part (LCD or E-ink) and steel be able to do whatever you want (and it's impossible with EE becouse of different native and input methods of e-ink and LCD).
We can also speak about "interaction" -- but it's also not a case 'cos it's supposed to work in both ways, thet you do an action and get an response (or action) in back. So in you examples interaction mean when you open an document with embeded media file on e-ink side, run it to view on LCD, but steel can control on media from e-ink. Or changing content of e-ink depending on what media you are viewing (or other actions which you're doing with media).

What we have now is called "exporting\importing" and "linking", but again there'n absolutly no integration.