Operational transformation is the main challenge in implementing PSYC as collaborative editing platform. As Google Wave appear to be positioning itself as a populist, lite groupware option, it would probably be prudent for implementors to be aware of the Wave protocol.
The negotiation phase of establishing a collaborative editing session would be similar to that for typing.
Examples of operational transformations would include diff and patch or any of the number of source code management systems or Wikis, but SCMs generally manage transformations with a granularity of a line. OTs for collaborative editing would have a token level granularity, where a token is either a character or a meta-tag.