Currently the only Google Wave server that is participating in federation is:
The following Google Wave servers are not participating in federation at this time:
As of this time if your domain uses Google Apps and you wish to federate with wavesandbox.com with your own wave service then you must disable the Chat service for your domain. We are looking to resolve this issue in the future so that you can have both services running at the same time.
Please also see the Issues List for the current list of open bugs.