The "bus stations," especially in the small towns and wide places in the road along the Highways of the USA, were like the Old American West History days when stagecoaches had to stop and get fresh horses and/or take on or let off passengers and other things carried on the stage.
In those stagecoach stops, one could often get something to eat. In the movie, the restaurant which was used was not exactly one of those bus station restaurants; it looked more like that the restaurant owner took over the bus stop franchise after the local bus station (owned by the bus company) had closed. I have been in those types of places back in the days when I took a trip on a bus, the first was back when I was 5 years old and the last was in January 1992, when I moved back to Tulsa, Oklahoma.
In the scene where Ennis is eating the pie and Cassie comes in with her current boyfriend, I am at a loss where they were headed when she saw Ennis at the table. Since they were going to the back of the building on purpose, were they going to use the restrooms first?