Plugin participant send information to another external application (Translator google)

He wants to communicate info from the plugin to an outside RTC application.

I'm not sure exactly what you're asking.  If you're asking how to get the owner of a work item from inside a participant, the following code snippet should work for you:

SubMonitor progress= SubMonitor.convert(monitor, NLS.bind(Messages.WorkItemCommenter_MONITOR_ADDING_COMMENT, workItemId), 100);
IWorkItemClient workItemClient= (IWorkItemClient)teamRepository.getClientLibrary(IWorkItemClient.class);
IWorkItemWorkingCopyManager manager= workItemClient.getWorkItemWorkingCopyManager();
manager.connect(workItemHandle, IWorkItem.SMALL_PROFILE, progress.newChild(20));
IWorkItem workItem= null;
    try {
           WorkItemWorkingCopy copy= manager.getWorkingCopy(workItemHandle);
           workItem= copy.getWorkItem();
           workItem.getOwner();

If this is not the answer you were looking for, please ask again. :-)