Judging by the image on the site — and the fact that the Fate/stay Night anime explores the “Fate” route pretty thoroughly — this movie is likely to be based on the “Unlimited Blade Works” route.
As ANN points out, Funimation are the current distributors of the Fate/stay anime. Whether or not they’ll license the movie remains to be seen, but the chances are pretty good, considering how aggressive Funimation have been of late. They picked up Phantom ~Requiem for the Phantom~ (based on the Phantom of Inferno Hirameki DVD game) really quickly.
Now, I wonder when we’ll see a Fate/Hollow Ataraxia anime…or even a game translation patch for that matter.