Your best bet is to deal with the maker of the Chinese trains in China and go in that way. Everything is controlled by the Cuban government and I don’t think they would hire outside for this.
You may want to offer your training services then maybe they might be interested in your product.
Selling anything to Cuba requires a long term commitment and most likely sales on credit (which is the Cuban government’s terminology for “give us the product then get in line behind everyone else for payment”).
Sorry but that’s just how it works.