Here are some numbers, although a very small sample, of my experience with this since the latest patch.

I have played a total of 13 games; 9 of which to completion(due to that other Land Grant Bug)

Of the 9 completed, the extra plot event happened in 4 games.

3 of the 4 games the extra plot went to the player in 2nd place:

2nd round: http://www.planetmule.com/hi-score-game/game?game_id=31676

7th round: http://www.planetmule.com/hi-score-game/game?game_id=31650

7th round: http://www.planetmule.com/hi-score-game/game?game_id=31512

1 of the 4 games the extra plot went to the player in 4th place:

6th round: http://www.planetmule.com/hi-score-game/game?game_id=31563

Here are two more from earlier today:

http://www.planetmule.com/hi-score-game/game?game_id=31585

http://www.planetmule.com/hi-score-game/game?game_id=31586

On the second one, one of the players who were trying to obtain the same plot left the game and we were able to continue..