It seems to be on in quite a few theatres - care of good ol' 'Flicks':
http://www.flicks.co.nz/movie/when-a-city-falls/

I went to the earthquake movie with my folks in Christchurch. We all cried quite a bit. My old man doesn't talk about it, so I suspect it was quite cathartic for him. Important to see it at a plex with good sound though I reckon. Agree -- it's not depressing, and more about folks holding hands after the crap hits the fan.