Heard about this on SiriusXM Road Dog. Pretty neat concept. I wonder if it will ever make it onto the smaller Western Star trucks? http://www.trucknews.com/equipment/western-star-shows-off-real-life-transformer/1003072068/
The reason it is on off road trucks is simply the fact of the added weight. You can already do some of this with a rolloff type truck, you just need the adapter plates, etc.
Never knew a rolloff was that versatile. I agree with the weight thing but I'm sure they can lighten it up some for a regular class 8.