Not only are their different dialects for different railroads, but if the post describing the C&TS hand signals are correct, then it is a whole different language.
But to answer your question, yes they do change. the hand signals not only change from Railroad to railroad but from Yard to yard on the same Railroad.
I know that Denver yard uses different hand signals than Cheyenne, Green River, Ogden and others. Each change because of different job conditions, spots, tracks, etc.
The rulebook reads that ANY hand signals can be used as long as they are understood and agreed upon by the crew using them.
Rick Steele