Yes, used in production for the Pixel C.

Is it developed by nVidia themselves though? Usually Nouveau is driven by the community.

NVIDIA has actually contributed some code to Nouveau to make sure that it will work with the Tegra platform (the graphics engine there, unlike on every x86 platform, isn't behind a PCI bus). Also, the display part of the Tegra SoCs is entirely different from what the desktop chips have and is controlled by an open source driver written by NVIDIA (tegradc).