Hi Gary,

There are very few things wrong with this branch, and of the notes I've
made below one's a vague suggestion, one's a comment and only the last
two are things that I think need to be acted on before this lands. Great
work by both everyone involved.

[1] 

Here:

56	+    def initialize(self):
57	+        super(BugSubscriptionListView, self).initialize()
58	+        subscriptions = get_structural_subscriptions_for_bug(
59	+            self.context.bug, self.user)
60	+        expose_user_administered_teams_to_js(self.request, self.user)
61	+        expose_user_subscriptions_to_js(
62	+            self.user, subscriptions, self.request)
63	+        expose_enum_to_js(self.request, BugTaskImportance, 'importances')
64	+        expose_enum_to_js(self.request, BugTaskStatus, 'statuses')
65	+

and here:

117	+    def initialize(self):
118	+        super(TargetSubscriptionView, self).initialize()
119	+        expose_user_administered_teams_to_js(self.request, self.user)
120	+        subscriptions = get_structural_subscriptions_for_target(
121	+            self.context, self.user)
122	+        expose_user_subscriptions_to_js(
123	+            self.user, subscriptions, self.request)
124	+        expose_enum_to_js(self.request, BugTaskImportance, 'importances')
125	+        expose_enum_to_js(self.request, BugTaskStatus, 'statuses')
126	+

the code is almost identical (save for where the `subscriptions` list
comes from. Might it be worth wrapping this stuff up in a mixin,
something like:

class StructuralSubscriptionJSMixin:
    """A mixin that exposes structural-subscription data in JS.
    
    Descendants of this mixin must define a `subscriptions` property
    that returns a list of the subscriptions to cache in the JS of the
    page.
    """

    def initialize(self):
        super(StructuralSubscriptionJSMixin, self).initialize()
        expose_user_administered_teams_to_js(self.request, self.user)
        expose_user_subscriptions_to_js(
            self.user, self.subscriptions, self.request)
        expose_enum_to_js(self.request, BugTaskImportance, 'importances')
        expose_enum_to_js(self.request, BugTaskStatus, 'statuses')

(Though that's only really worth the effort if we are going to do this
anywhere else, I suppose).

[2]

214	+            record = info[target] = dict(

I really don't like this idiom; it took me about 30s to work out what
was actually going on (admittedly, my headcold probably isn't helping).
I'd prefer it if we had this as:

    record = dict(...)
    info[target] = record

[3]

249	+        # It's a start.

A win for commentary, there.

[4]

435	+        # [{'filters': [{'filter': <....BugSubscriptionFilter object at ...>,
436	+        #                'subscriber_is_team': True,
437	+        #                'subscriber_link': u'.../api/.../~team-name...',
438	+        #                'subscriber_title': u'Team Name...',
439	+        #                'user_is_team_admin': True}],
440	+        #   'target_title': u'title...',
441	+        #   'target_url': u'http://127.0.0.1/product-name...'}]

I couldn't tell whether this is deliberately left in or not. If not,
let's lose it, if so, please add some comments to explain why it's here.

[4]

601	+            required=False))
602	+    @call_with(subscribed_by=REQUEST_USER)

There needs to be a blank line here to avoid confusion.