Canonical developers have hit the milestone of being able to run their "Unity Next" desktop atop the Mir Display Server. The work is still very early, but it shows for Ubuntu Touch they can swap out Android's SurfaceFlinger for Mir.
Unity Next is the next-generation implementation of Canonical's multi-form-factor desktop for Ubuntu written in Qt/QML. The Mir Display Server is still very primitive and not feature complete nor even on par with Wayland's features, but when using the latest code along with the out-of-tree Qt Mir back-end, it's possible to start running Unity Next.
Thomas Voß of Canonical posted proof of this early feat for switching out Android's SurfaceFlinger for the Mir compositor whereby they are leveraging the HWC 1.1 hardware compositor. The short video of Unity Next on Mir from the Google Nexus 4 smart-phone is embedded below.