It is now possible to subscribe to Ubuntu bugmail for the packages you care about, without having to use Launchpad (and subscribe on a per-package basis there). This is implemented as a new opt-in Package Tracking System keyword: derivatives-bugs.
To subscribe for all your packages, use keyword [email] + derivatives-bugs (as documented in the Developers Reference). You might also want to subscribe to derivatives (Ubuntu diff, etc. also opt-in).
Of course, if other derivative distributions are interested in providing such data, don’t hesitate to contact me or the Debian QA team.
Also, if you are like me and never remember about subscribing to packages you maintain, you can use that UDD script to check for missing subscriptions.