I'm not to sure about that one I allways thought they were below, and even if they are they still do need to find a suitable location to have gas tanks safely.
Well as far as I know inferno was planed to be how it is now, it had no buget cuts if I remember rightly so they obviously never wanted to finish it of, and I dont think theres room for it anyway what with there being a service road behind there and storage space. And the main thing it will come down to is money, it wouldnt bring them any in and it wouldnt be deamed worth it.