I got an email back from the architects. They told me the height of the observation tower will be 250 feet. The observation deck will be at 230 feet. So even at the observation deck, you'd be 3 feet higher than the control tower at ABIA.
He also told me that COTA wants any inquires about the project to go through them. He gave me the name and number of the media relations person at COTA. So if you have any questions about Circuit of the Americas, this person is the one to ask:
Media & Community Relations Manager