If you place a sign and label it, then click on Add world map tag, this works, and the text and icon is added to the world map.
But then delete the sign and the world map still shows the sign being there. this could be good or bad depending.
In my case it's bad because I moved the factory part over and the sign still says it's in the original position.
Just in case anyone is interested, you can delete it by clicking then pressing delete on the dialog.
