At CN, where the infamous Hunter Harrison (an ex carman, by the way), implemented PSR for the first, there has been a long standing "railroader" program where managers are encouraged to qualify as carmen and engineers. The point of it is to replace unionized workers in a strike. Just google it, "CN Harrison manager train riding". HH even has a quote where he jokes that the unionized employees eyeballs will pop out of their skulls when they see a train driven by a manager barreling down at them.
He repeated that formula at CP and you can google that too. Unfortunately, CP started "drafting" managers for train handling duties after a while and it started getting out of hand.
In fact, CN did use managers to drive trains during strikes when HH was in control.
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Side note: CP and CN are both very linear railroads. CP is essentially straight east-west while CN is a big T across Canada and down to New Orleans. Running those railroads like a conveyor belt, i.e. on a schedule no matter what is a lot easier than running CSX, UP, or NS on the PSR model. UP has some east west dedicated lines, but it's a lot more of a hub and spoke model. It's the U.S. too, unlike Canada, where all the economy and people are concentrated in one east-west band close to the border due to weather, we're all spread out. Point being, PSR is not something that's really meant for a UP style network.