I' ve yet to see a latios in the train. Have you tried the battle institute in nimbasa city? You just basicly fight 5 battles, single or double is up to you. As you win the battles get harder. Even if you lose, you keep going. And in the fifth battle, omg, its so hard. My friend played in the fifth battle, and his opponent had a freaking darkrai! He lost obviously, since he told that it kept using dark void. When I battled, my opponent had a zapdos, and I eneded up losing.