I don't know how good an idea, an ultra light wheelset for commuting, is in the first place.
But hey, since the question was asked...

And downtown toronto roads are just fine for tubular wheels. Once you get beyond the core of the city, then the roads really start to deteriorate, but even then, tubulars are much less likely to pinch flat. Not much debris around to puncture your tire either. rims will only dent if the tire inflation pressure wasn't high enough, causing the tire to bottom out and allow the rim to take the hit.

but if super light is desired... better than XR-200 would be edge 1.25 tubular, which is only about 215g.
That's 175g lighter than XR-200 and guaranteed to make your wallet... and bank account much lighter too.
If you built edge 1.25 around a mack hub rear and American Classic micro 58 front, I'm pretty sure it would be under 950g.