I don't know of any bzr command that does this, but it's actually very easy to script using the Launchpad python API. For instance:

#!/usr/bin/env python

import os, sys

from launchpadlib.launchpad import Launchpad



cachedir = os.path.expanduser("~/.launchpadlib/cache/")

launchpad = Launchpad.login_anonymously('find_branches',

                                        'production',

                                        cachedir)



try:

    project = launchpad.projects[sys.argv[1]]

    for b in project.getBranches():

        if b.lifecycle_status not in ["Abandoned", "Merged"]:

            print b.bzr_identity

except KeyError:

    print "Project unknown... 

Usage: " + sys.argv[0] + " lp_project_name"

So with python find_branches.py deluge we get:

lp:deluge

lp:~vcs-imports/deluge/trunk

lp:~mvoncken/deluge/ajax-template-dev

lp:~deluge-team/deluge/master

lp:~shaohao/deluge/0.9

lp:~damoxc/deluge/master

You can run wild with it and do things like sort by date_created, date_last_modified, or create your own heuristic for what branches are interesting to you. See:

https://launchpad.net/+apidoc/1.0.html#branch