Well, I finally got a chance to see the new chimp enclosure today and, in one word - fantastic!!
Those of you who had concerns that it was a "cage" - forget them. It is a cage but a beauty. In one corner it is at least 1 metre higher than the old cage and in other parts it is much higher than that. At least one of the boys uses the roof mesh to brachiate fearlessly at an impressive height. This is much better than any island or moated enclosure could ever be.
The floor plan of the cage is, more or less, in a Z shape so the boys can be out of sight of each other if they wish. The substrate is woodchips, ground cover vegetation and rotting logs lying on the ground. There are also horizontal logs above ground as well as very solid vertical logs. There is a small pool at one end which overflows into a little stream. Viewing is through 3 large glass window at different spots along the frontage. If the boys don't want to be seen then they have that choice.
Concerns about the vegetation by previous posters are also unnecessary. The vegetation in this cage is profuse. Grasses, bamboos, small trees, shrubs, vines, creepers - even vegetation now growing out through the roof mesh.
And, believe it or not - NO hotwires! Certainly some of the vegetation shows signs of chimpanzee gardening efforts, but not much. In fact, very, very little. The ratio of animals to area is pretty much spot on.
Going forward there will be some obvious changes if/when more animals are added. The vegetation could not be expected to withstand the onslaught of an extra couple of chimps.
And the cost - AUD1.2 million? I definitely think that a privately owned zoo would have got more bang for their buck but, what the heck - I'm happy that part of my taxes have helped to fund this magnificent upgrade to the boy's living conditions.
A belated answer to Pertinax's enquiry - I am not aware of any reason [apart from their age] why these two males could not be eventually successfully integrated with female chimps.