After generating a scale bar, it is placed in a MAP Legend layer. You can accept the default look of it, but majority of users will want to customize and style it to match their map.
Now I've just generated a simple scale bar. If you expand the Legend layer, you can see the object "MAPublisher Scalebar" is placed within it. This is a special object generated by MAPublisher and there is currently a dynamic link between the MAP View information (i.e. spatial information) and the scale bar object.