The solution to negotiating land purchase without eminent domain is to play "connect 4" by buying "options" - cheaper contracts that fix a price for a period of time but don't guarantee a sale. As soon as you have a connected path of options between A and B, you can exercise the options and run the line down it. You can spread the option purchases around a whole lot, so that nobody has an incentive to play awkward in return for more money, because you'd simply route around them.