They've outlined all of that, were just waiting on them validating it, they explained many mths ago that all of the UX layer will be open, only core/native apps will be closed.
As for openness at the lowest lvl(s) (the drivers etc), how do you propose that would/could work?
What's more important is all the glue in between, & so far they've indicated that'll be open, we're just waiting for all the detail.
Much of it's already very public thanks to progress with MeR/Nemo, but it just needs to be put into nice & shiny Sailfish charts/graphics, & the missing bits added.