Or they might not have known. If they had, I am pretty sure they would have pulled it. They have no reason to run the ad, they already got their money because ad space is prepaid. Just because we know about it, we cant assume everyone else does too.
They may be worried about legal aspects of not printing the ad...if ATA paid for the ad, then they may be sued if they dont show it, regardles of the current ata situation. I could be wrong though...its happened twice before.