Barry;
This must have been changed since our trip last May.
On the day we went to IOA, we each had open passes for Jurassic and the wait was for quite some time. So we went over to Bilge-Rat Barges and got passes for that and Ripsaw Falls, walked back and did Jurrasic, then went back over and used our passes for the Barges and the Falls. We did the open double or triple Express passes several times during our two days at USF/IOA.
As a matter of fact, I commented to my wife a few days later that this was another area where USF had surpassed WDW, in that they would allow three open passes, while WDW only allows one open at a time. I hope USF has not followed WDW on this policy.