So I was poking around Silverpine looking to take some screenshots, when I happened across this:
It's a fully functional Ettin-drawn carriage, traversing from north to south and back again. There are actually several of them, and they run back and forth regularly, stopping at each town. You can mount up and take a ride, and it will work like an impromptu flightpath.
I uploaded a video of it here (I apologize for quality, it's still processing):
+1 for horde ingenuity. =p