Remember that air is made up from air molecules (well, oxygen and nitrogen molecules) and the interaction of the train with the air is ultimately down to collisions between air molecules and the surface of the train. When the train is moving the air molecules at its front bounce off faster than they hit, and these faster moving air molecules in turn collide with other molecules and accelerate them as well. The end result is that the front train is surrounded by a blanket of faster moving air molecules and accordingly the pressure of the air in front of it rises. Air flows away from this high pressure zone, which causes the wind as the train passes.
When viewed in this way I'd say that "the train pushes the air out of the way" is a pretty good description.