Actually, it is.
http://thefinancialbrand.com/19864/m...-credit-unions
Quote:

People withdraw money from a mobile ATM machine set up in a van, Friday, Nov. 2, 2012.
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Chevy Chase Bank did it, too:
That being said, if I came across one just sitting along a street at night, I wouldn't use it. If it was part of a town's fair or some type of event, then I would trust it more.