The NTSB investigation found that after 13 cars from the westbound grain train derailed, the train’s emergency brakes were applied. At that point, the eastbound oil train was 18 seconds away, traveling at 42 mph. The oil train was likely moving at about that speed when it hit the grain car lying across the track, the NTSB said.[/unquote]
I would opine that the crew of the grain train didn't know they'd derailed (ie, everything was still upright) until the derailed car apparently hit the switch (as reported by the signalman), at which time it went cattywhampus, breaking the trainline (initiating the emergency application) and fouling the adjacent track.
The linked report itself says that at the time of the emergency application, the oil train was a mere 18 seconds away, doing 42 MPH. The collision was going to occur. Period.
Give the crew of the grain train several seconds to recognize the brake pipe was headed for zero, plus time to reach for the radio and make the emergency broadcast. There is no way that broadcast would have changed the outcome, even if the oil train had dumped their air.