Just called UA reservations for an itinerary for the end of the month. Booked on CO with CO codeshare, but UA flights. Neither the CO.com or UA.com would show the seat map. CO said to call UA. UA said to contact the codeshare airline. Called UA res and was told that the system was still being worked on, but he put me into E+ seats anyway. I guess I'll see later this month whether I am put on the first class list...