You have to watch as these can vary by railroad and the legend would be either in the rulebook or special instructions.
Since it only shows one mixed train as far as Bates, I'm assuming this is towards the end, so if it was after 1940 "O" would mean OIL as fuel for the 250/251. I have seen timetables that list T for turntable and Y for Wye, but also where T means turning facilities. By the looks of it, Y here may mean Y or turning facilities (assuming So. Baker still had a turntable, but where was the wye to turn the mallets?) It looks like the wye at McEwen stayed in until late. Unless Y means yard limits?
I had assumed that the dispatcher would have been at So. Baker but evidently while the crews probably went on duty there the dispatcher and general offices must have been in the Baker depot. (BTW - the SVRy Baker depot still exists but is across the tracks from the in the former UP depot location.) Dr. at Austin I assume notes there is a doctor available. The station column typically would have telegraph station codes (two letters), D for day operator, D-N for day and night operator, YL for yard limits, and R for train register.