This is used to add contents into the "Proposed for publication" panel displayed for sections. This panel will only be displayed when there is at least one element (article, site, news item...) in that section that has been proposed for publication.
It is called from ecrire/exec/naviguer.php:
pipeline('rubrique_encours', array(
'args' => array('type' => 'rubrique', 'id_objet' => $id_rubrique),
'data' => $encours));