Funny you should ask, because I was just looking at the October calendar for IOA/USF to see what was going on. The hours for USF that night are consistent with the hours of every single other HHN night:
I also checked the IOA park hours, and they have a normal closing time of 8pm - so there's definitely not a two park buyout:
So it looks like there's either going to be some kind of special, separately ticketed premium night, or someone/some company dropped A LOT of cash to buy out only USF or only HHN for one night during the peak of haunt season.