Though Ya Ca Mein has become a New Orleans favorite, it's not particularly unique to that city. Yatcamein or yetkamein or yat gaw mein (you run the possibilities) is a similar dish available in many cities, including Cincinnati and Chicago. The recipe is really not very different from ramen (etymologically "ra mein" or "lo mein").
Also, the nickname "old sober" is a bit weird. It doesn't really make grammatical sense as the name you'd give a soup used as a hangover cure. Possibly the word "sober" is a corruption of "soba," the Japanese noodle, since this is a noodle soup. But then, why is it "old"? Was the soup originally a way to use up leftover (or old) old soba noodles? Or maybe it was requested by people who asked "give me some of that old soba."
Clearly more work needs to be done on this dish.