Reflecting/Refracting an imageplane:
Select the imageplane (get it in the Attribute Editor)
-the easiest way is usually to select the camera, and go through the
same way as you created it.
-or go into component mode and select 'Image Planes' under the '?'
now you can select it in the viewport.
Under it's 'Render Stats' turn on 'Visible in reflections' and/or 'Visible