While AeroVironment is Nissan's preferred vendor, Nissan dealerships have the discretion to choose the brand of charger they install. Nissan makes a 44kW DC Quick Charger unit that is sold by AeroVironment and costs under $20,000.
The Fiat deal came about in an interesting way. Nissan had asked AV to put together a dealer package so that when people buy a Leaf they also have an easy way to get a home charger. Since this package was still on the books, AV recently took it to Fiat in preparation for 500E sales. We should know more in a few weeks.