Currently the AccuRev plugin does not create snapshots as part of its processing. There was a feature added by dwms to the trunk while back which provided a basic level of functionality, but I took it out temporarily to get some other changes released. I still have these changes, and I plan to revisit this feature and give it a proper go.
It should work like this: at the build level, you can enable "create snapshot for build" in the advanced section of Source Code Management. Possibly some options for how to name the snapshot (e.g. what suffix - date/time, transid, etc). It would use the name of the configured stream and append to it to get the snapshot name.
When a build is triggered, the snapshot will be created, and then Hudson will pop the source and perform the build. I don't think it makes sense for workspaces to be available for snapshots, "create snapshots" and "use workspace" may be mutually exclusive.
Snapshots could get out of control over time, so there needs to be a way to trim them, much like Hudson jobs trim old builds. Probably just a # of snapshots to set. If that is the case though, we may want a way to specify that a snapshot should be "kept forever", and a way to delete snapshots manually.