Originally Posted by
Imperatrice 
as a bizarre follow-up, while i was at a friend's birthday party tonight, the XABF in question proceeded to text me out of the blue FIVE TIMES asking to see me.
if this had happened two months ago i might have considered leaving the party early in order to see him.
instead i followed the plan described in my initial post, and told him that i couldn't see him right now! and i feel really proud of myself for having done that.
I don't mean to sound suspicious, but since you didn't engage him on the train, maybe he is nervous that he is losing his hold over you. It has been my experience that childish alcoholics may not want to have you around, especially if you have a problem with their drinking, however they also don't want you to really move on in case they want something from you, even if it is only gratification for the ego.
Well done but be careful if you do see this person. Keep it short and public if you can--coffee shop, etc. Good luck!