Wow. This looks pretty damn interesting. Essentially, Battlefield 40k is a Battlefield 2 modification that places you in the Warhammer 40k universe. That's right. A warhammer 40k shooter that allows you to be something OTHER than Tau (though you can play as the Tau if you want), but there will be no less than SIX races: Space Marines, Imperial Guard, Eldar, Tau, Orks and Chaos Space Marines - pretty much something for everyone.
Anyone who wants to learn more can visit the official Battlefield 40k site
here.