Does Liam Neeson give voiceover for Batman in Batman Begins?

^{I wasn't sure if this holds as an actual answer, but I'll write it anyway. I'd rather say the burden of proof lies on the question's theory here, but in lack of a more "official" answer for now, here's my reasoning:}

No, he doesn't.

If your only premise to the question is the fact that Batman sounds a bit similar to Liam Neeson in that scene (which I won't even deny), then I have to say this doesn't seem to be enough for suggesting such a quite unlikely possibility. Even in light of a yet missing denial by the film-makers, there just doesn't seem to be any reason at all why Liam Neeson would dub this scene (or any Batman dialogue for that matter).

Now why does he still sound a bit that way? You have to consider that Batman's voice is largely distorted in the first place. And especially in that scene he is standing quite far away, so he has to shout and there's quite a bit of echo from the alley. All this contributed to his voice not sounding like his normal Bat-voice but a bit more low and clean, or "Neesonesque" for that matter.

^{(On top of that, it also sounds to me as if this was filmed and recorded on location and not overdubbed later, which would definitely speak for Chsritian Bale talking himself, but I might be wrong with that.)}