ICO told me this was a possible outcome of my interview. They said that after the class was full they would rank the alternate list and then if spots opened up they would fill them with people from the alternate list. These spots would come from students they accept not taking the seat they were given in the class for whatever reason (most likely going to another school).
They said they could take people from that list as late as the day before classes start. I don't know for sure if this is the same for SUNY, but that is what I know.