

The moment you buy it, that track now has to operate by the rules, which means it's going to lose you a lot of money. The reasons you buy another railroad are either because it's part of the scenario, because you need a ton of track built that would cost you too much to build yourself in the limited time available (again, a scenario reason), or because you just have a vendetta against those dirty cheating AI players.

I haven't paid close attention, but it seems to me they get a stipend plus inflated delivery charges and pay less maintenance. All this is because the AI doesn't have to make money the way you do, they just get it. First, their track tends to be laid out much more inefficiently than necessary, second their stations tend to need either upsizing or moving into proper positions, and third, their engines tend to be the worst possible choice - the AI chooses engines based on unloaded top speed and doesn't consider the terrain. Buying another railroad is usually a bad proposition if your goal is to make money.
