Grand Canyon had originally intended to run 90+ passengers per car behind steam. When they discovered there was a market for first class service, the dome, lounge and parlor cars provided far fewer seats per car, increasing train size beyond what their steam engines could handle by themselves. The change to diesel was a necessity as much as a cost cutting measure, since many steam trains had to be double-headed.

Rumor has it they will do the 1472 day inspection/repairs for the 4960, meaning that once it's done, they need to run it an average of 98 days per year at minimum to get their money's worth before the 15 year limit expires.

IMHO The biggest issue with large scale professional entertainment operations is their management spends more money on advertising, customer service, catering and gelato machines than the train itself, because they do not understand rail and how outrageously expensive rail is to maintain.