Linked library items via MovieClipLoader?

Question

So, some of you may have run into this before. I know there
is a known issue with importing an SWF to a MovieClip using
LoadMovie - in that, any library items in the SWF that have linkage
IDs can only be attachMovie'd within the MovieClip itself, and not
in the main timeline (or any other timeline).
However, I'm ok with this limitation.
I have a project where I'm creating an empty movieclip on the
main timeline, called "clip_1".
I then use a MovieClipLoader object to load an external SWF
("buttons_1.swf") into clip_1.
This works.
However, buttons_1.swf has several button clips with linkage
IDs set. What I want to do is, after buttons_1.swf has successfully
loaded into clip_1, then do something like
clip_1.attachMovie("btn_play", "play", 1);
where "btn_play" is the linkage ID of a button in
buttons_1.swf.
This does not work... and it probably should given that
apparently some people get a similar thing to work with
loadMovie(). I want to use MovieClipLoader, however, because of the
built-in error catching and completion features of that class.
I cannot use the "runtime sharing" workaround for this,
because I will have a potentially unlimited, unknown "button" SWFs
that will be used. The main movie will load the appropriate button
library at runtime, but I can't know in advance what all the
libraries will be, and after the main movie is published, ideally I
cannot go in and edit it again (want to have it dynamic as possible
from the beginning).
Any help would be appreciated. I know this is a confusing
issue.

Answer 1

Oops! Missed some quotes:
var mc = this.createEmptyMovieClip("test_mc",
this.getNextHighestDepth());
var mclListener:Object = new Object();
mclListener.onLoadInit = function(target_mc:MovieClip) {
// child movie contains MCs with linkage IDs
// attach an instance of "testclip"
var _d = target_mc.getNextHighestDepth();
target_mc.attachMovie("testclip", "clip"+_d,
_d,{_x:30,_y:30});
var mcl:MovieClipLoader = new MovieClipLoader();
mcl.addListener(mclListener);
mcl.loadClip("child.swf", mc);