Well, in response, I have to agree to disagree. Jacksonville is denser than you think...mainly in the inward parts of town where there are thousands willing to ride public transportation. Commuter rail would be on a CSX owned rail line that comes from Amelia down to St. Augustine, a city that has expressed interest in being further connected to town. Even in St. Johns and southern Duval, where it is all sprawl being built, there are limited highway and road choices that will become superclogged as everything gets built, unless every road is widened to Atlanta size (we dont want that), and I would bet that developers know this and would be willing to build transportation hubs.
The CSX line that runs from Amelia west to the N-S main line that would be used, I heard only has one or two trains on it a day, so that wqould not be a problem.
Given that the city will find a way to deal with CSX (which I have heard cannot be dealt with easily), a nice commuter rail line in Jacksonville with ten to twelve stations should not cost more than $150 million. Far better than riding a "high tech" bus system in twenty years for more than a half BILLION dollars.