The general pattern of delegation of responsibility in Ubuntu is as follows:
When we identify an area of the project ("Foo") that needs more focused and specialist governance we try to create *two* teams: one of Foo Members who have made a substantial and sustained contribution in that area, and one governance group, like a Foo Council.
The Foo Members team is created as a member in Ubuntu Members, so anybody who is added to Foo Members becomes an Ubuntu Member by virtue of that. We try to populate that initially with folks who meet the requirements for membership and are known to understand that area well: they are typically people who are voices for calm and competence, and heavy lifters in the area Foo.
We then seek nominations for the Foo Council. Anybody can nominate anyone, including themselves.
The group who is delegating authority then puts together a shortlist of the nominations. We *always* retain the right to shortlist, i.e. we do not put forward all nominees to the poll. Shortlisting means we exercise a level of judgment on the candidates who get to be considered. We then generally put the shortlist to a poll.
The poll can take many forms. Sometimes we nominate a single candidate, and the poll is a vote of confidence; we would not appoint someone who fails that test. Sometimes, it's a runoff, when we nominate m+n folks for m seats, and then we generally use Condorcet voting.
The structure isn't always this straightforward, but the pattern is consistent. For example, the LoCo structure is richer than this, because you have a LoCo council and then LoCo leadership teams per loco. The Forums governance structure has a Council, Moderators and Members. IRC has a Council, global ops, channel-specific ops, and members. The development structures are more complex because as Raphael described we have several different ways to delegate upload and commit permissions. But in each case you'll see the same basic pattern: the delegator nominates leaders who are put to some sort of poll of pre-identified contributors in the relevant area.
In my capacity as founder and head of the project, I play the role of nominating candidates for the two most senior bodies: CC and TB.
I'm on record as having a strong desire to see Canonical balanced by non-Canonical voices on both groups. In the CC we have been able to achieve this: we have a very deep pool of leadership talent with skill and insight into the social and governance aspects of the project. There are more non-Canonical folks than Canonical folks on the CC.
In the TB, we haven't achieved it. But not for lack of trying. The TB roles are widely viewed as requiring generalist distribution developer skills that apply to only a small group of people in the world. You'd need to be a long-standing, active Debian or Ubuntu developer (though I suppose an excellent contributor to another distro might qualify, they'd need to demonstrate insight into Ubuntu and Debian that would be highly unusual in a top developer who spent most of their day on another distro).
I would estimate there are probably less than 100 people across Ubuntu and Debian who might qualify. We have a standing ex honore seat on the TB for a representative from Debian's Technical Committee, currently filled by Bdale Garbee of tie-die fame. But other than the Debian representative, all the posts are filled by folks who work full time on Ubuntu and Debian. There are not that many of them, and those that are, mostly work for Canonical. We've held several rounds of nominations, I don't recall ever having removed from the shortlist someone even vaguely qualified who did not work for Canonical.
So, I hope you'll grant me the benefit of the doubt: there's no desire to lock the TB down to Canonical, there just have not been folks willing and able to step into those shoes who didn't. As keybuk said, mjg59 served brilliantly if acerbically for some time, and is missed and welcome back any day (subject to confirmatory poll ;-)).