*sugar*, that's definitely a possibility. In fact, you're almost certainly correct, since we know for a fact that the car is downloading map tiles, since you can observe that occurring. I guess I hadn't thought about how that means they can't abstract the labeling away, which means you can't control label rotation. Damn.
The real question is if the existing hardware can support SVG/vector map storage and rendering, which, maybe? It might not be a hardware limitation, versus it being an artifact of the times: in 2012, I don't know if GMaps was allowing 3rd parties to use the more advanced vector mapping. But realistically, the whole mapping product is a unique hybrid and who knows how the hell it's implemented.
