It would be their internal overhead.
To call it “administration” is an oversimplification. The overhead encompasses much broader costs; these are normally indirect costs that are in support of the operation but not directly assignable to the operation. The president's salary would be a part of the overhead, but it would be a smaller component of that amount. It is fringe benefits such as health and welfare costs, Canada pension plans, company pension plans, accounting costs for the company, and inventory costs for the material. It would be the first-line supervision costs for the supervisors and foremen at the shops.
All of those are in support of the maintenance. The maintenance could not be undertaken without this supporting cast or supporting role provided by the railway.