The broken neutral via the earthed connection could perform in the same way as above.So something is missing.Please see post no.49.Can you furnish the transformer neutral earth resistance value to proceed further?
Not saying the resistance of the grounding electrode will not matter but even if we assume it to be zero you still have the resistance of the grounding electrode at the service location. Lets say it is 10 ohms which would be considered a very good grounding electrode.
Now lets place a 720 watt 120 volt (20 ohm) resistive load from one line to the open neutral that will seek a path via the 10 ohm grounding electrode. You will have 20(load) plus 10(earth) = 30 ohms of resistance with 120 volts applied. Using Ohms law this gives you a current of 4 amps.
This will give you a voltage drop of 80 volts across the 20 ohm load and a voltage drop of
40 volts across the 10 ohm earth path.
Everything bonded to the grounded service conductor will operate at 40 volts above earth ground. There may not be as much voltage in the area very close to the grounding electrode but that area will be very small especially with only 40 volts of drop. If you were to have direct contact to bare skin across this potential you will feel it.
If you have a water pipe grounding electrode and it is continuous to the neighbors place and is also bonded to their service with a 'good neutral' then its resistance will be very low and will become an alternate path with almost no voltage drop, just like the open neutral conductor would be if it were not open.