Here's some good information: https://www.cdc.gov/hantavirus/index.html
Bottom line: There is a always some degree of risk regarding exposure to rodent droppings.
I would weigh the pros and cons of purchasing the trains. If it's low to medium end,common postwar,I would likely pass.
Me? I worry more about dealing with venomous spiders! I am a recovering Arachnophobiac in a 12 step program.
Ricky