Are the chargers really that smart? Do they communicate with the car and know the make/modle/year etc?
Which brings up something else. Could a company potentially build a step-down converter to use to charge my Leaf for free? I'm not really sure how much hardware it takes to step down voltage that significantly.
Yes, the Tesla charging port has a data link that allows Superchargers to speak directly to the battery's firmware. There is almost certainly "Tesla DRM" built into the handshake between the S and the Supercharger, although like all DRM it could probably be reversed engineered and compatible systems created.
That's a lot of fun when you are trying to copy a Blu-Ray, less fun when you are dealing with 100kW.
SAE J1772 has a data pin, yes. It's how the car communicates rate-of-charge.
The Supercharger uses a different plug, though, which I don't know anything about. The voltage (440v) and speed indicate DC charging, which J1772 doesn't support. (The Leaf uses the CHAdeMO connector for DC charging)
In a standard charger, the car has to negotiate a power level before there is any voltage on the charging pins at all. http://en.wikipedia.org/wiki/J1772#Signaling However while the Model S comes with a J1772 adapter, I'm sure your Leaf doesn't have a "Tesla" adapter.
