Happened to me last week. Four of us had MCI-DFW-PVR award tickets on AA, and the MCI-DFW part canceled, leaving no good options to make either a DFW-PVR or an ORD-PVR flight.

So AA called over to UA and rebooked us there. I immediately called UA, gave my MP number, and got us all booked into E+ for the flights. When I got home, I noticed that the segments posted as full Y, complete with the appropriate 2x bonuses for the 25th Anniversary promo.

And for what it's worth, Ted was lovely to PVR. He was happy to see us and he was on time. Although E- was packed, we were able to sprawl out across an entire row in E+. FA's even chased off a couple of seatpoachers. It was much lovelier than the packed AA Mad Dog coming home. RAR!!