Thanks to @Jake for following up on this thread and my sincere apologies to @FunkyGibbon for not seeing your question until now.
The tubes only go to the staircase which was intended for keeper interaction. The staircase is located inside the new American alligator exhibit, though at the time this photo was taken (first day new gibbon exhibit opened) that area was empty and awaiting refurbishment. By the way I saw the completed alligator exhibit for the first time today and posted photos in the gallery (though I think this staircase is cropped out of the photos).
For the record this exhibit now houses black and white ruffed lemurs and there are some problematic reasons why the gibbons are not there (as well as my personal opinion on why it should never have been built). I will not say any more here, but interested parties are welcome to start a private conversation with me.
