(at around 20 mins) Mike, when calling the Control Center, says, "Umpire to Shortstop...Umpire to shortstop. Over." The man at the other end responds. "Shortstop this is Umpire. Go ahead."
While Mike and his partner are hiding behind a rock, the camera moves slightly behind the rock and you can just see a neatly open gap in the rock indicating it is a prop.