With all due respect, I think it is safe to say that you do not know much about Australian railways, and your basic research skills are non-existent.Hey, whoa, calm down there. All the man did was ask a question in the hope that those more knowledgeable than him would provide the correct answer, which you've done
A basic look at Wikipedia (I know, not the most reliable of sources, but accurate enough in this case) will tell you that there were substantial modifications, and that the XPT goes nowhere near what the IC125 does.
If you were to do even basic research before posting, you wouldn't be cluttering up these boards.
I know that there are some who say "These sites are there to ask questions, and to obtain answers", but we are talking about the internet, and the answers are out there and readily obtainable even by those who do not know how to search.
Sorry for my rant, but every time I see posts like yours, I see red.
The forums provide a great platform for people to discuss and share knowledge. I have no particular interest in the XPT or the HST, but I enjoy reading people's thoughts and insights towards them. I'm sure there are others here who don't necessarily want to put the energy into researching themselves but are happy to pick up knowledge along the way through questions like don_dunstan's.