There can NOT be a grounding wire or rod outside, it is impossible. If there were, since the neutrals and grounds are both bonded together in the panel box and therefore leave the panel box bonded together there could be no way to ever separated those paths on the outside? Impossible.
So either the neutrals and grounds are both grounded outside (I have read that many years ago all neutrals were "sent back" to the elec utility through the ground but I dont think that happens any longer (but hey what do I know.... not much) OR they both travel back on the neutral wire (grounds and neutrals).
Either way it seems very strange and "not right" but heck what do I know (not much it seems).