It's actually an actor by the name of Bruce Greenwood. If you watch the "behind the scenes" featurette on the "Justice League: Crisis on Two Earths" DVD they actually interview him and give a small sample of his performance. Here's a link to the first part of the featurette.
I will add that he did a fantastic job as well. Am I the only person who thinks poor Kevin gets dragged into too many animated Batman flicks? Don't get me wrong, he is awesome, but not all animated features are alike. This can lead to things getting weird if the Batman from movie X sounding like a completely different Batman from movie Y especially if neither movie are in the same canon as each other.
I agree that a little variety is never a bad thing. Usually...lol. I mean, I wasn't a big fan of William Baldwin's Batman in "Crisis on Two Earths" but I did like Jeremy Sisto's portrayal i n "New Frontier". And it's not like we won't ever be seeing Conroy as Bats again. He'll be voicing him in the sequel to "Arkham Asylum" and most likely in future "Superman/Batman" animated features if they make more sequels from the comic series. We were lucky to grow up with Conroy as the Batman we grew to appreciate through the DCAU and a little change is never a bad thing. Usually...lol. But I'm very much looking forward to Bruce Greenwood's portrayal in "Under the Red Hood" next. Then Conroy again in "Apocalypse" in September.
I'm spoiled, I guess. Conroy can do "Bats" until he's an octegenarian...Well, he's already given us a glimpse of how he might sound as a more "mature" Bruce Wayne in "Batman: Beyond," now hasn't he? :>)