Yes, that's pretty much the size of it. If we go into STATIC discharges (e.g. lightning strikes) then it gets a bit more complicated, but as far as normal power distribution systems are concerned no current can flow to ground so long as there is only one point of the system connected to ground.
And yes, if you have a generator which has no ground connection you could take a wire and ground either either conductor and nothing would happen -- No sparks, no flash, no current to ground (except perhaps a very tiny leakage current due to the aforementioned capacitance effect).
