|Its a pity I missed this thread while it was happening.
I live in a society that is still rapidly urbanising, but unfortunately has a high crime rate. New villages, so to speak, are created on the outskirts of cities, with private roads (and high perimeter walls) mainly to restrict access to criminals. In essence the citizens buy a piece of land as well as a share in a company (or trust) that builds/owns the roads. The shareholders/trustees decide the rules of whom to let in, speed limits, the operational levies etc. This works very well. By buying the property in the first place you agree to abide by the majority vote (and thus the nature of existing/prospective shareholders is often a buying criterion).
I see no reason why this should not in essence be extended to roads connecting villages etc. and eventually to superhighways. (A "tree with branches" analogy is useful here). Of course, a way out of our current council owned roads would have to be found - probably not that problematic.
As to eminent domain - I presume this is the state's ability to seize the property of an individual. Its obvious to me that this is impossible in an Objectivist society - for how would it be exercised without the initiation of force (back to principles). So I would have to support the right of that one person who refuses to sell to the superhighway company.
A simple way around the problem (faced by the superhighway entrepreneur living in a society without the imminent domain law) is to purchase options to buy property from the whole community at a prescribed price. Once he has options with a suitable route, he exercises them, buys the properties and builds the highway. If insufficient people take up the options he needs just up their price. If an entire community refuses even to buy the options then the need for the highway must be questioned.
As an aside, to me it's obvious that there is no market value without a willing buyer and willing seller - just try and trade in an unlisted or small cap stock.