Thanks, Keith. That makes sense now, here they have a combination of numbers and letters and numbers. The numbers often mean the locations and the letter/number combo like 3BW7 it departs on a Tuesday from Brisbane to Wollongong and is the 7th train in the timetable from Brisbane.
Pacific National run Grain train 5938 bound for the Manildra factory in Bombaderry, at te end of the New South Wales South Coast Railway line. Seen here passing Jannali Station.