grounding trucks gives a false sense of security. If your relays are set correctly and you get a large enough rise in fault current, a grounded truck will trip the circuit.
At the end of a long line it will see it as load and just pump more current to the circuit. Your gonna be crispy either way if you are in contact with that vehicle when it becomes energized.
Current will take ALL paths back to its source. Not only the best. ALL Paths! That means if you are in contact with a grounded vehicle when it is contacting a source of energy, and you are at a different potential, current is going to flow through you! You are in series with the circuit.
That poor apprentice wouldn't have been helped by EPZ unless the building was bonded to the truck, and there was a bonding mat to stand on as well. Touching a truck and a metal building is going to put you at different potentials. Then you will get a voltage rise and subsequent current flow. subsequent death!
Ground your vehicles. Hopefully no-one is touching it and standing on the ground too. As I said, a false sense of security!
You need to Look up! Talk to the operator. Wear your rubber gloves, and wearing 20 KV rubber boots would be an added plus. An epz mat bonded to the vehicle with a rubber blanket to make the transition on and off of the mat.
Use your brain! Don't be another person talked about in the past tense.