It’s a good question — it seems that no, they’re not. As you can see here, companies like Mercedes are not only leaving these screens open for use with their own systems, they’re also leaving them open to Android in the future (though details aren’t clear there).
All of this sort of led to my reference to the Rokr. We’ll see how well Apple likes playing on other’s hardware. They do it a bit with the Apple TV, but as you note, this is someone else’s touchscreen.