They are lying to you! Nissan has a part that flashes the firmware in the head unit. It's supplied by Clarion as an SD card. It has a Nissan part number, all US dealer Leaf specialists were sent this to perform the updates. If they flash this with the EU spec version, and then replace the SD with the EU maps your nav will work. I'm less sure of the TCU, as there could be a difference, but this is also flashable. Worst-case, all you'd need is the TCU replaced with the EU-spec version.
It's Clarion all the way. Clarion is at least partly owned by Fujitsu TEN, I believe. (Part of the global Fujitsu group which is huge!)
BTW, There is a possibility I may be able to replace many of the built-in functions with an application that runs on
LEAFSCAN™. So all settings and displays, other than Nav, would be viewable/adjustable on
LEAFSCAN™, thus making it possible to at least ditch the crappy built-in head unit and install a good aftermarket.
LEAFSCAN™ has an SDIO slot that can accept a WiFi adapter, so it may even be possible to replace carwings remote functions (and add more) at least when the car is within range of an access point. For me this would easily handle 95% of the remote functions I use carwings for.
This will be a future enhancement, if possible, but not in the initial release.
-Phil