I have a marathon slick on my toronto commuter and a snow stud on my calgary winter bike - as far as I can tell the grime/guck/salt has completely obscured the reflective sidewalls - the reflective coating seems to be worn out in spots too. I'll try setting up a viewing sometime to see if any of it is visible, but given the dirt, I doubt it.

The reflectors on the wheels are visible AFAIK.