I believe the gates are controlled by a "predictor" grade crossing system which is closing the gates as the train approaches, and then raising the gates when the train slows and stops at a station before entering the crossing.
The train then has to leave the crossing slowly, allowing either the "predictor" system, or (if very close to the crossing) the "crossing island" circuit to again lower the gates. The engineer then has to allow at least 20 seconds (from the crossing activation) before the train occupies the crossing, which may even mean stopping the train. This results in slow departures from the station stop; and sometimes motorists becoming impatient and violating the crossing when they don't perceive the train as an immediate danger.
The "DTMF" (dual tone multi frequency) control discussed in the article (article calls it "BTMF") would allow the engineer to initiate the grade crossing signal/gate closure as the train is leaving the station stop, thus eliminating the very slow approach to the crossing. Motorists are more less likely to violate the crossing when they can sense the train accelerating. I don't know if the system would allow an engineer to prevent a gate closure; the "predictor" system should keep the gates down until the trains location, speed and deceleration rate indicate it will stop short of the "crossing island."
Useful links:
Wkipedia
How Motion Detector and Predictor Railroad Crossing Detection Works (personal page; some good description, some very technical)
Ross