is there a bonus for agg hatching during the event?

It's 5x, not double...

I should know this answer, the event was live during my lunch time walk. I was {t,w}alking with a friend and was in full auto-pilot catching mode. (Friend does not play). I even hatched an egg. Totally forgot to look at the XP. I did notice the extra fire and ice mons, so I was not completely clueless.

Full-on auto-pilot is when I just see mon, catch mon, repeat. I really don't pay much attention. I assume what it might be like for PoGo players, except I do momentarily see the mon that I'm catching.