Thank you so much for posting this little gem!
Not sure if this was for a publicity stunt or if the transformer needed to go on some historic short line to get to where it was going.

I have a schnabel and this load was a heavy one. Schnabels usually do not have smooth brakes, just the parking or emergency brakes.
As such typically they use heavy cars with good locomotive controlled brakes.

However a steam lok does the trick very well , and those grades dictated that the train need both power unit in places.
This is why the first part of the clip did not have the steam lok providing power.

Many thanks! Now any of the rivet counters that make fun of me....I show them this video....

FYI. The only reason that they have the passenger and box car is to separate heavy weights of the 2 loks and the weight of the transformer on a bridge or culvert.