Nope! wrong, they do not belong to Bungie
There are 2 "quasi official" Warthogs in existance and they both belong to Weta Worshop and technical Microsoft and were built here in New Zealand, and generally spend a lot of there time here in Mirimar.
I have had the privelidge along with Belkor to have some time with one of these vehicles and their creators.
The shell is indeed Fiberglass construction, and every detail is near perfect.
they only thing they could not replicate was the independant suspension, and that was due to budget and time, but it does have 4 wheel steering etc.
the tires and rims had to be specially made.
I can't remember what Chassis they based it off but think it was the Bronco.
Weta were pushing to license it as a collectible with Microsoft, but at a price tag of $150,000 USD+ they didnt see much uptake.
Apparently they still get offers from people with money to make them, but they are not allowed due to licinsing issues.