I'm not great at this, but there's definitely some LFO on the pitch of it, relatively slow attack, and it doesn't seem to have that long a release on it either (going by when he lets go of the notes)
When I first heard this I thought it was a vocoder, kinda sounds like a choir sample layered with something else, although from the responses in the thread about the group that can't be true, haha.
Maybe some chorus might help with it - it sounds very wide to me. I've been messing with sylenth but haven't bothered using the right notes so can't really do all too well, haha.
Sylenth1 should definitely be able to get very close to this though, assuming it's not using any samples.
EDIT: Scratch that, re-read the thread. I'd be willing to bet there could well be a choir sample (nexus/omnisphere/alchemy all have these) in there, especially going by the subject matter
I'm gonna be trying to get this for ages now, hah