I have not seen this scene in a while if I am recalling right, it is a real train. We do see the flashing lights of the train across Michael's face. Sollozo keeps on talking regardless, he and the capt appears not to bothered by the train. The train roars in Michael head because he is more interested in making his bones than in Sollozo's trite speech. So he really does not hear Sollozo. The train comes in better focus.