[thomasahle]

I'm pretty sure it didn't, though I can't find it explicitly for Alpha Go. For Zero they specifically mention that it took the self playing a long time to learn ladders well.

[espadrine]

I can confirm that the original 2015 Nature paper for AlphaGo mentions setting ladder capture / ladder escape bits as input to the neural network.

cf. https://gogameguru.com/i/2016/03/deepmind-mastering-go.pdf, Extended data table 2