No attempt to modify the Curacao Treaty has been made as of yet, Daedric is right; The debacle you're referring to was the Sirius Summit.
I don't see a reason they can't bring up the Curacao treaty, but I don't know what they would want to change about it. It's about as slanted in favor of OS&C as it can be. OS&C have no need or benefit from managing all of Cortez, and trying to keep it policed. Thus having an agreement where Liberty and Bretonia do that for them is exactly what OS&C should want.