Thanks - I thought the 'switch' to airport control occurred much prior to GA's showing up - and I guess more importantly airport upgrades resulting in a shot at a good Y seat will occur at the gate anyway (upgrade list) making seatmap useless as its apparently blocked at that time. I did use the seatmap when I was in the AC about 2 hours prior to departure to identify a slightly improved seat and then had the AC agent generate a new BP, so I guess it has some utility prior to GA taking over.