I believe the bug being referred to is "9862
Separate group for
ipblock-exempt on en.wikipedia".
AB provided a patch which added an ipblock-exempt group, which a user
could be added to to be exempt from IP blocks (but not from username
blocks), but this was rejected because the power wouldn't be available
to bureaucrats (the software only allowed stewards to perform such a
feat). Then Simetrical made a patch to implement Special:MakeIPExempt
which would allow bureaucrats to put users in the group, but this
patch was rejected because it was considered too messy to use yet
another Special: extension. Bug 6711 addressed this, and is now
resolved. It adds a Special:Userrights page and exactly who has the
power to do what can be configured on a site by site basis. So now
that 6711 is resolved it seems to me that AB's patch should now be
accepted. Then, any wiki running the new version of the software can
allow assignments to the ipblock-exempt group using
Special:Userrights, so long as the appropriate $wgAddGroups line is
added to the config file.
Once the patch is accepted, it'd be up to the individual projects to
decide who, if anyone, should be allowed to assign users to this
group. Presumably for wikien it'll be the bureaucrats, who will
assign/remove users to the group after a successful !vote.
Alternatively, sysops could be trusted to assign/remove users to the
group, either after a successful !vote, or under their own judgment.
Individual projects can already decide that. The patch that hasn't
been accepted is just one to add the ability to enwiki, that's one
project, and it's a project that has not made the decision to add the
ability. The MediaWiki code already has all the functionality it needs
in this matter, it simply needs to be turned on in the settings for an
individual project. If a consensus is found to exist to turn it on for
enwiki then the patch will be accepted, but that consensus does not
exist (or, at least, hasn't been shown to exist).