The movie is not based on the 2013 comic event.
Kevin Feige mentioned the following during an interview with Empire in July 2013.
http://www.empireonline.com/news/story.asp?NID=38238
Q. How long has this been in the works? The comic book run is only just wrapping up...
"It's not that [run's] story, but it's that title. It's been in the works for seven or eight months... There are some things in this movie, that you'll see in 2015, that arise directly from casual conversations Joss and I had on the set of the first one. 'Would it be cool if...?' 'That would be cool!'"
"We came up with a few titles, but every month a new comic book appeared, and that's a great title. Age Of Ultron is a great title. We had a few other 'Of Ultrons', but that was the best one. So we're borrowing that title, but taking storylines from decades of Avengers storylines."