The interview and context is better in this article which puts it into full context...
http://www.oxm.co.uk/article.php?id=846
So what will 360 owners love about Unreal Tournament III?
Rein: It rocks. It's so much fun to play on console. There's a little bit of auto-aim like on Gears... what I like is none of our success on console has affected our games on PC. We have mods on UT for PlayStation3 and...
What about the 360 version?
Rein: To bring mods to 360, we're going to have to make some serious changes.
So you're not going to include them?
Rein: Oh, it's going to happen but 360 is a closed system so we have to work with Microsoft on that.
Can you tell me the reason why Unreal Tournament III became a timed exclusive for PlayStation3?
Rein: I just did.
The mods?
Rein: Yeah, the mods. That's what makes it sell for so long, what keeps it played years down the line. I can understand the frustration from 360 owners but it's not going to go away. Five or six months down the line, Unreal is still there. Are they going to come late to the party? Sure. But the game will still be there and that's when the best mods will start coming out too. We've had talks with Microsoft about it but I don't think they're ready for it yet. Sony's been ready. Don't forget we only announced UT was coming to 360 in... January, so it's not that big a surprise.