You might want to take a look at the jQuery Sonar plugin:
https://github.com/artzstudio/jQuery-Sonar
I’m trying to do the same thing with my progress bars and the sonar plugin is used on lazy load wp plugins. All you have to do is bind their event to the wppb when the document is ready (instead of animating) and then, when the event is called, unbind it and animate.
Pretty simple concept. Might be worth de shot.
