> ... the Greek MLW A-504 is the first American-built (this includes
> Canada too ;-) ) diesel locomotive to cross the Atlantic three times. >
> Is this right, or wrong? I would be glad to get some references in
> verifying the accuracy (or not) of this claim.
It's possible, but I can't think of a reference. There have been locomotives that crossed the ocean twice, but I can't think of any that made the additional trip. In past, locomotives shipped out of North America tended to be specialized designs with light axle loadings. This meant that there was usually no interest in bringing them back, since they weren't usable on North American railways. If a used locomotive was exported, then it was usually because it was no longer wanted, so again there was little motivation to ship it back.
I wonder why aren't many American modelers
> interested in export locomotives...
Probably because they don't see them regularly. Out of sight, out of mind. In the case of Montreal Locomotive Works, their locomotives were typically covered in tarps after they were built, and then loaded in ships right near the factory. That meant the locomotives weren't seen until they arrived at their destination.