The TV show Extra did a web-only feature on the Los Angeles Papaya King truck (possibly for the benefit of transplanted Warner Brothers employees): http://extratv.warnerbros.com/2011/04/papaya_king_hot_dogs_invade_la.php
It includes a video that features this truck: http://mobimunch.com/PapayaKing_4db99c327fdc9
I note the truck only charges $2.00 for a frank with onions, kraut or relish. A combo with 2 franks and a drink is $5.50. The video shows they are using natural casing franks.
As the the bricks and mortar restaurant, I have this theory that you need a lot of foot traffic for a Gray's or Papaya King to succeed. Los Angelinos, correct me if I am wrong, but I recall Hollywood and Wilcox having a lot of foot traffic. As long as this restaurant chain puts in a good manager, this place should succeed.