Currently, Zend_ProgressBar_Adapter_JsPush, just works if the large proccess (that wil be monitored by the progressbar) runs in a hidden Iframe. I've started a improvement to make possible to do it with a ajax call to the larg process. It is very simple, I have just removed the tags, and the parent object in the return of the the finish and notify methods. I've included a $_ajaxAccess propertie too. If you set this propertie to FALSE (using setAjaxAccess() method), the class will work normaly, if you set it to TRUE, it will work with ajax. In the moment, the improvement, only work in firefox, but I'm working to portate it to other browsers to.
I hope it could be usefull.