Most teams use 3D printed parts. They are perfect for the evolutionary nature of cars.
You'll find that, it's used mostly for non-structural components, or for wind tunnel models, and tooling.
As for the Ultimaker 3, I've seen teams use similar printers for mocking up assemblies, before the real parts are made, but mostly, they are industrial level 3D printers for the serious stuff.
Hope this helps!