I booked an OZ award ticket JFK-ICN-BKK on LifeMiles and on a whim decided to see if I could display the reservation on Avianca's web site (avianca.com). I was able to display a couple LM bookings I had using NH, TG and OZ, and was surprised to see that I could display the seat maps for all three carriers on the Avianca site and select seats, even on OZ.

I would recommend, though, that you first check the seat maps on ExpertFlyer (you can display them for free) to see which seats are blocked out. OZ seems to block a lot of the cabin in F and J, but the seat map displayed by Avianca doesn't show which seats are blocked, so you might keep requesting seats and getting rejected if you try confirming seats that are blocked. (Avianca immediately advises if a seat number cannot be confirmed.)

Anybody game to try displaying their OZ reservation (which was not booked directly with AV nor with LifeMiles) to see if they can select seats on http://www.avianca.com? If so, on the AV home page, click on Electronic services, choose Ticket Status and enter the e-ticket number or RLOC and see if it is displayable, and if so, can you view/choose seats on OZ?