Originally Posted by serfty
Welcome to the other side lonely flyer. By all means do the AA Plat challenge, but at best that can gain you is AA Status equivalent to oneWORLD sapphire. i.e. AA Plat === (for example) Qantas SG. Both are Sapphire which you already have via another oneWORLD Carrier!
There are subtle differences, especially in the States. For example, a QF SG can access AC's in the states in some circumstances where an AA Plat may not.
As I read it,
Lonely Flyer does not have any status at the moment (QF NB). He will get OW Sapphire via AA Plat Challenge, and was then wondering about access rights for his wife as a guest once he achieves it.
As you pointed out, AA Plat won't give lounge access on purely North American itineraries despite it being OW Sapphire.