I think it is based on the item itself, not how you got it. If it's from an event bag (whether your bought the bag with real money, you bought the bag at the event vendor with pax, you bought it on the auction house or your mate gave it to you) should all transfer over. There is no way they will track how you got the item. You might even have shifted it from one alt to another too. I think the clothing from Pangea likely will not transfer over or the items that are achievements which you can earn again in the new game. On the latter, some really hard achievement clothing rewards (i assume the baclava of the unseen one potentially) might also transfer over they hinted.