I'm using Avid BB5 Road discs with Dura Ace STI integrated shifters. It works perfectly. 160/140mm rotors front/rear.

I'm not sure if you're aware that there is a ROAD and a MOUNTAIN version of Avid mechanical discs.
The calipers of the mountain version are black and the road version are silver.

The next generation Sora STI levers will be able to work any kind of brake, mountain or road. The upshift knob will be gone, replaced by a conventional lever.