For whatever reason, everyone is celebrating, etc, and out trots the kicking unit???? At this point it's a 1 point lead for Hamilton with 19 seconds left. They end up making the extra point to up by 2. Great.
My win probability model did not like the choice to kick the XP, giving the 2 pt attempt about a +2.5% gain in win probability if they went for two, regardless of if they actually were successful or not. Marshall Ferguson called it best when he said that the "1 point convert doesn't really get you anything."
Let's walkthrough possible scenarios to see how that 2.5% lines up. We can assume Ottawa's motivation is constant whether down 1, 2, or 3.
Obviously, a kick return TD basically wins the game for Ottawa and should have no impact on our (Hamilton's) convert choice.
We're going to make some very imperfect assumptions here, but it's really just to validate the above 2.5%. Both scenarios will have the same assumptions, so it should be a pretty fair comparison.
Let's say Ottawa has a 15% chance to move the ball into FG range, and they're going to make that FG ~65% of the time. We also will give them a 5% rouge chance. If the game goes to overtime, we will assume a coin flip (50%). We can also assume that Hamilton has a 56% chance of making a 2-pt convert, and a 94% chance of making a 1-pt convert.
Ottawa: 56% (Hamilton made 2-pt conversion) * 15% (drive into FG range) * 65% (make FG) * 50% (WP in OT) = 2.7% chance of Ottawa winning.
Ottawa: 44% (Hamilton missed 2pt conversion) * 15% (drive into FG range) * 65% (make FG) * 100% (Ottawa wins the game) = 4.29% chance of Ottawa winning
Ottawa: 44% (Hamiton missed 2pt conversion) * 15% (drive into FG range) * 5% (rouge chance) * 50% (WP in OT) = extremely LOW. negligible.
Ottawa: 94% (Ham made 1pt convert) * 15% (drive into FG range) * 65% (make FG) * 100% (Ottawa wins the game) = 9.1% chance of winning for Ottawa
Ottawa: 6% (Ham missed 1pt convert) * 15% (drive into FG range) * 5% (rouge chance) * 50% (game goes to OT) = extremely LOW. negligible.
If you compare these, going for 2 gives Ottawa a combined ~7% chance of winning, regardless of if you make it or not. Conversely, going for 1 gives Ottawa a ~9% chance of winning. It is very clear that going for 2 is the correct choice for Hamilton.
It is also worth noting that if Hamilton just manages the clock correctly, this choice basically does not matter.