Family Guy and Underworld... this is like a marriage between two of my favorite things. Anyway.. we must get to the bottom of this. Very curious indeed.
By the way, they showed a preview (about 10 minutes) of this episode at Star Wars Celebration IV... which was in May. And it included this clip, but Ring Road was not in the video at that point. You can still see the preview here:
http://www.milkandcookies.com/link/62681/detail/
So yes, the episode has been around for a long time, but they must have added Ring Road somewhat recently.