I agree with those who say that Madara activated Nagato's ability to awaken the rinnegan, similar to how Itachi awoke Sasuke's magekyou as a trigger against Obito. I have a feeling that Kishi will have a hard time explaining this. Especally, how Madara managed to survive so long when he said he died after SHORTLY awaking his rinnegan.[/QUOTE
Sasuke DID NOT get the mangyeko from Itachi, he awakened HIS OWN mangyeko. Itachi transplanted a ONE SHOT amateresu into Sasuke, not a Mangyeko, if it was like that then either Itachi would also have blaze release, or Sasuke would also have Tsukiyomi, their Manyekos are different.
Look at Sasuke's eye when the amateresu self activates on Tobi, it looks exactly like Itachi's.
But when he goes to fight Bee, his eye is completely different to Itachi's, which shows that he has now awakened his own mangyeko.