Phone, US-based. I had the CO Plat line connect me to what I think was the UA elite line and started talking about the email sent to CO flyers about calling to get into the UDU queue. The agent said he knew about it and had done it before, then listed my reservation for UDU. My reservation now shows as upgrade pending. This was my fourth attempt to get into the UDU queue; on the other attempts, the UA agents gave all sorts of excuses why they couldn't, from "we don't have the capability" to "you have to do it at the airport."