I wouldnt think you can get away with putting a patten on that
You could not patent the concept of whistle steam. However, the arrangement of the items to impart whistle steam to a hobby locomotive could hypothetically patented. However, such a patent would be a "method" patent. This would encompass things such as how big the exhaust hole is, how long is the tubing to deliver the smoke, where the drive fan is, where the electronics are. Method patents are the weakest. If someone accomplishes the same task but with a different method, for instance different length of tubing then that would be a work around of a method patent and would not infringe. However, it has to be shown that the different length in tubing is important to the function and not just to get by a patent. If MTH came up with a different method, then that would not infringe on Lionel.