what I use (plain java )
final IWorkspaceManager mgr = SCMPlatform.getWorkspaceManager(repo);
// get the list of streams
            IWorkspaceSearchCriteria streamsearchcriteria = IWorkspaceSearchCriteria.FACTORY.newInstance();
            streamsearchcriteria.setKind(IWorkspaceSearchCriteria.STREAMS);
            // loop thru all the streams on the src system
            for (IWorkspaceHandle iwsh : (List<IWorkspaceHandle>) mgr.findWorkspaces(streamsearchcriteria, IWorkspaceManager.MAX_QUERY_SIZE, null))
            {
                IWorkspaceConnection stream = mgr.getWorkspaceConnection(iwsh, null);

                // if this workspace is a stream
                if (stream.isStream()
                // AND it is in the same process area as the seleted project
                        && stream.getProcessArea(null).getItemId().getUuidValue().equals(owning_project.getProjectArea().getItemId().getUuidValue())