I've been using that tubing along the fender to hang a tool roll and Christmas decorations.
It also provides a place to cram shims when readjusting the rear fender on the UCE's. A couple of people have had trouble with a shimmiy that turned out to be an accidentally spring-loaded fender because of factory mis-alignment. (Only a few bikes, I think)
LOOK OUT IT'S COMING THIS WAY!