I've noticed several times when flying UAL and listening to Channel 9 that after touchdown at O'hare, we will go to the penalty box and declare to the ground controller that "United 123 doesn't have a gate!" However, I never hear the transaction where the pilot finds this info out. How do they learn of this? I know it isn't the ground controller telling them, they don't have time and it isn't their job. So after landing does one pilot stay w/ the ground controller and another radio in to the ops tower on the ramp area to let them know they are in? Is that how they find out that there is another plane at the gate and that they have to go to the penalty box? I also noticed it today at OAK during the security breach. There were more WN 737s than gates and they all had to idle out in the distance until one opened up. At OAK, there is no ops tower, so who communicated to all those WN planes and made sure they were up to date and where to go when things came open?