What I got out of this episode was this:
The finding of the plane was genuine, or they wouldn't have shown us the actual underwater footage and the 'surprised' crew that found it.
The pilot is not the pilot we know, they made that clear from the drunk pilot's dramatic reaction.
Naomi knew the Losties might be there (I was wrong about this one, I thought she was out of the loop!

) but Abaddon insisted that the passengers were confirmed dead.
Charlotte was not surprised at the Dharma find in the desert and even seemed to know that the collar would be there.
The variety of people they sent to the island clearly shows that they know what to expect on the island; ghostbuster, anthropologist, physicist, talented (though often drunk) pilot.....
So the answer is clearly that the plane and bodies were planted by Dharma or related company to divert attention from the island OR the plane is actually 815 from another timeline and either the drunk pilot did fly the plane or the original pilot wasn't married in this timeline......
I guess this doesn't get us anywhere, does it?

Sorry!