I figured out what was going on, and regret taking your time. Let me explain what I did in pseudo-code. Hopefully it is helpful to someone else.
var myTL = new TimeLineLite( );
myTl.add( TweenLite( $('.something'), 10, {
opacity: 0,
onComplete: function( ) {
myTL.pause();
}
}), 0 );
myTl.add( TweenLite( $('.something'), 10, {
opacity: 1,
onComplete: function( ) {
console.log( "do I get called?" );
}
}), 10 );
myTl.eventCallback( 'onComplete', function() {
console.log( "all done!" );
});
myTl.progress( 1, false );
The pause in the first callback prevented the second callback ("do I get called?") from firing. Confusing me was that the timeline's onComplete ("all done") was called.