you are absolutely right, I have also heard that diesel cars are not allowed..is it true in anyway. Because I was looking to take my own scorpio for the trip.In my opinion any sedan will have problems. You have to be very lucky to get the clear route. Expect lots of under body scraps and stone hitting underbelly's.
Also you have to very careful while crossing even a minor land slide, and if its a major landslide, pray fore you cross it.
I am not de-motivating as I have seen M800 and Fiat Padmini covering this stretch, just you have to be very careful and lucky.
Else this what you will have to do, if your car stalls in the middle of landslide. Though you will get ready help from trucks. I had to tow it back with help of a trucker.