Afterany batch process could show progress in real time but we lack the feature in batch api to raise messages as they come in. In fact, batch operations' progress message are based in:
$context['message'] = "Doing 1 of 3."
A proper change would be to improve drupal by changing this array based storage to something that allow drush (or watchdog, or ...) to hook and get the messages in real time.
It seems we have some oportunity to catch this in drush http://stackoverflow.com/questions/787692/operator-overloading-in-php