Yes it can. It comes with a threaded cover for the bearing stub. I currently have my spare wheel on the roof. You just have to remember not to enter any car parks! This is easy for me as I rarely need to do so and I used to carry a spare wheel permanently on the roof of my SIII so I'm aware of it being up there.
Actually, despite being worried that I would find moving the Rijidij spare wheel carrier out of the way all the time, I was surprised to find that it didn't bother me at all. I only removed it to fit a bike carrier and just haven't bothered putting it back on.

