Oh yes very uncommon indeed, I've never seen one, our team that does the games etc. wear white dress shirts, and the kilt for the men, and white dresses for the ladies usually with a tartan sash.

For our dances here it mostly a modern casual look, a golf shirt, or dress shirt with the kilt, the ladies get away with murder. Then of course there is the Tartan Ball where it is black tie, however White tie ie. a Montrose Doublet has been known to be worn, I will wear mine to the Tartan Ball this year.