When you select multiple items via a checkbox control in your dialog, there is no way to directly output them again in your templates. I tried for ages to find a way to do this using just the taglibs, but I had to resort to a small scriptlet in the end:

Iterator hubs = Resource.getLocalContentNode(request).getContent("hub").getNodeDataCollection().iterator();

while( hubs.hasNext() )
{ 
out.println( ( (NodeData)hubs.next() ).getString() + "<br />" );
}

Maybe there's a better way, but this works for me. This should also work for radio button controls.