There are some community choirs that do mainly classical music.The definition seems to be, as Saro says, an inclusive choir with no formal selection process or auditions. In folk/world music choirs, there's normally no requirement of musical experience or sight-reading ability, but I think this is not necessarily the case with classical community choirs. If you're going to do some of the big choral works, you need at least most of your members to be able to read music, or you'd spend years learning the parts. It may be that such choirs do use the music and just allow a certain percentage of the members to be "passengers" while the rest learn from the score. I just don't believe a whole choir could learn Bach's B minor Mass or Verdi's Requiem aurally, without anyone using "the dots".
I'd be interested to hear of others' experiences.

Marje