FEC just lacks the resources for something like that, so it'd have to be government backed.
Can you imagine what a few Genesis locomotives would look like flying across those bridges. Some American tourist would be poking along in their cars behind some old rusty car or truck and flying by on Amtrak would be some international tourist, looking out the window of all that blue ocean and all those fools in their cars behind this old clunker poking along.
They could easily run 2-3 trains daily up and down those tracks. Maybe more and offer a light freight service, post office would love that!!
And the car traffic would stay the same. You know, Americans - We're always a little slow to catch on.