[quote name='karsh']On [as], they only could get Ready Steady Go for much of FMA. Thus, for the first 41 episodes, RSG was the opening for [as], despite there being three openings during that run in the actual version of the show. Well, they recently got the rights to the last FMA opening, Rewrite by Asian Kung-Fu Generation. And it kicks ass.[/QUOTE]
Actually, the explaination for that one is that Sony, owner of the Tofu Records label which distributes the domestic L'Arc~en~Ciel albums, wanted exposure for the band's music on TV, and cut a deal to only show that intro. It just so happens that a domestic version of Asian Kung-Fu Generation's second album, Sol-Fa, got a domestic release by Tofu Records back in October, which is why they're now using that intro.
And now you know!