FWIW, my 9071 order placed on 9/19 never actually said backorder when calling 877. Just "preparing to ship" online, and "your order is being processed" when calling. Oddly, I have a secondary order number (?) that starts with 7223 that is also an option to check on 877 which says backordered. I don't know which one I should be tracking. The 9071 number is what shows up online.
BTW, it is safe to say most 9/12 pre-order 6+ folks have gotten their phones, or at the very least gotten a shipping notification from AT&T?
Aaaahhh... Someone else with two order numbers. When I placed my initial order, I received an email telling me my order number was 7230#####. (I ordered on an iPhone 6, not a 6+, on 9/20, so my order number was higher than yours.) My "Terms and Conditions" email had another order number, 907###########. The 7230 order number has been reporting "backordered" from the beginning, and the 907 number has been reporting "being processed" also from the beginning.
This last Saturday, I received an odd email from AT&T, "Information about your AT&T plan". That prompted me to call the 877 status number. The 907 order number still reported "being processed", but the 7230 order number reported "being processed" and also provided an expected shipping range (the same as I'd received all along.)
Sunday afternoon, I called the 877 status number, but now the 7230 order number reported that the order had been shipped and provided a tracking number (FedEx). The 907 order number still reported "being processed" (it still does today...) A few hours later, I received another email from AT&T, "Your recent ATT order status" with conformation that the order had shipped, and providing the tracking number."
Yesterday, the tracking number showed the phone had been "picked up", but didn't arrive at the FedEx facility until today - now it seems to be moving within the FedEx system.
Again, this is for an iPhone 6 (Silver, 64GB), not a 6 Plus. I just wanted to let you know what the two numbers meant in my case, so that you'd know what to expect. Good luck to you and all the other 6 Plus PreOrders!