NWseaflyer: I do not believe the rules for how codeshares will work have been finalized. You will all note that this introduction covers ONLY mileage earning, status perks, and club access -- not mileage redemption, codeshares, or *gasp* upgrades.

Here's some info from the other side of the force.

NW's info is linked above. Most questions can be answered from these public sources.