Also appears to be the official vehicle of the FBI, CIA, Secret Service and basically any cool or interesting federal or state agency. I asked a spooky guy just the other day why this was after noticing that this rule held true even in Baghdad where they have to be imported at great expense. He explained that the large overbuilt chassis makes them very suitable for the aftermarket body armor and bulletproof glass modifications. Also, the companies that do this like to stick with only one or two models to simplify design and manufacture, which is why they don't often bother with different model vehicles.