No, Vacaville is not the end of the line. There is an In & Out in Chico and in Redding.
I see what you mean, though. They should be able to get a truck up there regularly. On the other hand, if they're getting the buns on a local contract, and tapping into the same contractor the prison uses for the meat, you could have some problems Fur Shur.
BTW, been to Redding. Have some cousins out in the mountain ridges around there. Flying over the region is an incredible experience.