I have not studied history of the GNR outfit. May at the time it was built, the wild west was still pretty much uninhabited.
One can put together a right of way very cheaply using tiered options, one for entering the agreement, one when the right of way is completed, and a third for when the option is exercised. With a system like that, the neighbors end up putting the screws to the holdout to gain that next tier. At that point, people start exploring land for speculative buys assembling rights of way, doing deals with Indians, etc WAY out in front of the project. Free enterprise distributes risk, just like fascism concentrates the rewards.
Eminent domain at the Federal level was for "forts, dock yards, arsenals, magazines, and other needful buildings." NOTHING ELSE.