i came across this today - each green had two holes cut into the green, one with a flag in it and the other without a flag. these weren't "shared" greens, but it was a nine-hole course. i'm assuming they didn't replug the old holes when they cut the new one since all the grass is still dormant? i really have no idea.
the question is, what happens when/if your ball finds its way to the hole w/o a pin in it? do you remove it from the hole and place it in a position no closer to the actual pin, but in a manner that ensures that the old hole isn't in your line of play? i would assume that to be the case, since it is a man-made, immovable obstruction.
You are correct. The hole is a hole made by maintenance and as such a GUR.
Rule 25-1 states:
Interference by an abnormal ground condition occurs when a ball lies in or touches the condition or when the condition interferes with the player's stance or the area of his intended swing. If the player's ball lies on the putting green, interference also occurs if an abnormal ground condition on the putting green intervenes on his line of putt. Otherwise, intervention on the line of play is not, of itself, interference under this Rule.