Having read this entire thread, as well as a similar thread posted last fall here and on the rypn board, I have to say this. Let's all keep one thing in mind: there are a whole lot of native locomotives of various gauges out there, stuffed and mounted, that need preservation. I daresay there are locomotives in the lower 48 that deserve our attention and our dollars without going to central or South America or Cuba or Jamacia to find more. I would bet that any locomotive from south of the border will need a new boiler right off the boat.
Unless someone has a specific for-profit venue at which they intend to operate a repatriated export locomotive, the money spent in bringing it back to the states, fitting a new boiler, and doing all the other stuff necessary to make it compatible with current standards is wasted dollars.
As someone mentioned, railfans are a particularly provincial lot, and they are tightwads to boot. So unless you are buying Powerball tickets and have a pipeline to the winner's circle, this discussion is a waste of bandwidth and brain cells.