Richard; It is patrol tunics modified and retaining, as you can see in the photo, the Armour chain mail epaulette.
The tartan is MacKenzie; a fact of economy when raising the band. The drummers wear the cavalry overall.
A little bit of history here https://www.strathconas.ca/pipes-and-drums. I was on the California trip, filling in for the bass who had taken ill. We were asked by the 15Fd Regt Band to join them for two US service Change of Command ceremonies. Wonderful experience - especially the Seabee Mess.