I would say that they mean he is tough (assuming Bob Copeland is a boxer). I'm not a boxing fan but I think boxers get punched in the face/jaw a lot. So to have an iron jaw would mean someone who could take hits to the face and not go down easily. Just another way of saying he's a tough boxer. If Bob Copeland isn't a boxer but just an announcer, then it could mean that he could talk a long time on tv/radio and not get tired--another variation on being tough.

They probably either mean he has a strong jaw, or that he is quick, witty, and serious with his speech.