I do not think they will ever breed in this enclosue, no places to hide, no shadow - both are enormous important for a breeding success of owl-faced-monkey.....
I tend to agree with you This is a shy nervous primate species and even if they can survive them longterm, may find living with Gorillas stressful too. Being a deep rainforest species they need plenty of shade and climbing equipment, not evident here. I don't like to see such a rare valuable species being exhibited like this.