FWIW I've been investigating this myself.
iWork doesn't actually work from a WebDAV server. It is simply able to copy things over from one. Any docs copied over then live in iCloud. So updates don't appear on the WebDAV server.
The dream of seamless interoperability with Macs is still a dream until better iCloud integration happens, presumably with Pages 12 and Mountain Lion. This is a shame. 🙁