It seems like the UA Elite Desk is able to overide whatever mechanism is trying to charge for Premium Seats.
I have spoken to the UA Elite Desk twice now and each agent was very happy to help, even for something as mundane as seat selection.
One agent was having trouble with my reservation and we were chatting for a bit while she waited for her supervisor to fix my record. In chatting, she mentioned that she was looking forward to showing CO Elite pax how great UA can be. It turns out that she reads FT and knows that some CO PAX (myself included) are really unhappy about joining up with UA.
If more UA employee are like her, this marriage is not going to be a disasterous as I once feared.
Dan