If he says it's a Download exclusive then they've probably signed a contract saying they can't do it elsewhere...at least not at the competing European festivals. However, since they're rehearsing the songs I can see them adding it to other setlists too.
Sky Arts usually have a few hour shows covering Download Festival, they'll surely broadcast some of LP's set.
Also, I saw LP at Download 2004, before they played it was Sum 41, after Sum 41 played LOADS of people left, it sounds like the organisers think Hybrid Theory will be a pull for the Download punters.