Scenic Rys operating format from 1972 to 1979 was running 4 days a week. The train ran straight through from one end to the other. I think it was Sat, Sun, Tues, Wed. You rode the train one way and rode the bus the other. You could ride the bus before or after your trip, depending on where you started from and where the train was. Scenic had a fleet of school bus-type vehicles they bought new to handle the passengers on the highway portion of the trip. The buses had two problems: 1.They were rear engine and had trouble getting sufficient cool air through the radiators at slow speeds climbing the hills. 2. They bought gas engined buses. They worked for a few years, then started having severe engine problems. They had big International V-8 gas engines that just couldn't take the abuse. They were blowing up engines on a regular basis. Someone told me the busses got to be as expensive to run at the trains were. I have a hard time believing that, but reliability was certainly an issue. The jump in gasoline prices in 1979 really hurt. So... in 1980 they came up with the 2 train format of one train a day from each end, and sold the busses to the first likely sucker to come by. With some modification, it is the same format used today.
And yes, they used to do photoruns for the public at Big Horn. Eastbound trips were runbys done at the siding and wye. Westbound trains did one a mile or so west near MP 301. When I rode in 1978, I road east, and the train stopped at Big Horn for about 15-20 minutes for everyone to get out and stretch their legs, but there was no runby.