Apparently the kernel developers at Canonical get a lot of leeway to diverge from the corporate party line and get to use git setup on corporate hardware to better sync with the git using upstream project. Clearly Canonical is willing to let developers use git over bzr when its the better tool for the job, as in the case of kernel development. Not-Invented-Here syndrome can be a tough thing to pushback on for any organization which prides itself on the work being done by its own in-house development teams. Canonical isn't the only organization that suffers from that. There is more than enough NIH going around. Kudos to the kernel team for being able to get the tools in place on Canonical infrastructure regardless of the politics and the lack of direct integration with the normal Launchpad-based development workflow for Ubuntu. When GNOME moves to git as well, hopefully Canonical will extend the same luxury to their desktop experience team so they can work more closely with GNOME upstream. There's no reason to think Canonical won't allow it, they already allow it for the kernel.
The real question is, will Canonical extend the same sort of git repository services to the rest of the Ubuntu community who need to collaborate better with upstream projects as the upstream migration to git accelerates. Debian packaging is starting to see noticable migration to git, and unless Canonical integrates git services into its Ubuntu workflow for all contributors, that move is going to make it more difficult for Ubuntu maintainers who want to collaborate more closely with Debian and vice versa. Too bad Launchpad's Soyuz isn't going to be opened so that Debian and Ubuntu contributors could worth together to equip the Ubuntu build infrastructure by extending it with git services as a side-by-side option to bzr.