4:46 into their video detailing the making of "One" Axwell says "we've put it through Ozone, and it goes, like, 'BOOM! What happened there?' *laughs*"
The video was filmed in August 2010, which predates the release of Ozone 5, so they are very likely using Ozone 4.
"I do use Ozone 4 on my master out but I really only use the EQ and the limiter. The EQ is just so easy to use and it’s been part of my arsenal for years. I’m looking forward to trying out Ozone 5 very soon!"