Look at your radar. When your icon isn't slightly greyed out, any sweep by a UAV will pick you up.
in other words... if its the normal yellow you can be seen on uav. apparently climbing ladders you aren't safe ;/ anyone know any other times you can be seen when you probably shouldn't? i think when stopping to get a care package you can be seen as well.
if anything black ops 2 promotes even more camping if no one has ghost and the way uav spam if going decent player will see enemy location and just wait for him to go around corner... seen mutikply killcams where player will ads right before i go around corner.