Patch notes here: http://na.cityofheroes.com/en/news/p..._2012_live.php
It had a number of things (including fixes for boleros and a lot of Hybrid bugs). I'd actually guess that the summer event was patched in a while ago and simply not activated, but I could be wrong.
Earlier this week (yesterday?), I got prompted to update CoH when I opened the launcher. What was that update? I'm thinking it was the Summer Event.