Got it!... Took me all day, but  made a SOAP-call from Groove to a custom Radio Userland Web Service using Groove's SOAP-API.

Dave Winer in his Web Services Tutorial: "the mind bombs are only beginning."

So, this means a Groove Tool can retrieve info from anyone running Radio, but the service could also make Radio do usefull things like 'editPost' etc... Soon, with Edge Services,  Radio-clients can make SOAP-calls to a Groove Tool...