I think your solution works, sorry had to reply quickly in the console so just did a quick test, need to check it properly
TweenLite.fromTo(myTimeline, 1, { time:0 }, { time: 0.5, onComplete: function () { myTimeline.pause() } })
Did a few more tests in the console and seems to be a good solution, here's the tested code:
TweenLite.fromTo(myTimeline, 1, { time: myTimeline.progress() }, { time: 1, onComplete: function () { myTimeline.pause() } })