Bloggers have been hocking the ability to do this for a few years now. It's not exactly a secret.

Right now everyone gets something out of this:
1. AS is clearly selling miles for more than they pay EK for the tickets, or they wouldn't be selling miles so aggressively
2. EK clearly doesn't have a problem with AS taking seats on its planes -- or places a greater value on having a AS on its side as a US carrier in favor of EK's access to Open Skies when such things are debated -- not to mention EK gets to decide on which dates and routes it wants to give AS access to tickets

Perhaps at one point one of those calculations will change and the deal will end. Until then, party on.