In the class 1 RR industry what is the general percentage of the total cost of being an operating road that platform payroll represents in relation to the costs of maintenance of the fixed plant and rolling stock and fuel?

I'll bet it is quite a bit lower than payroll's share in, say, BART's total cost. So the AAR might be willing to keep one operator on board to mollify public opinion and safety concerns but with the recognition they did not have to, so as to keep pressure on the unions.

BART has to go driverless so it can divert that cost to hiring security and enforcement staff. Freight trains probably do not have very many thugs, pervs, junkies nor homeless on board.