At WMSE we have Project Managers that will take the responsibility to keep the tasks on Phabricator updated for their projects. Each project team will remain some flexibility on how to best structure it, but will adhere to the overreaching structure for the association: https://se.wikimedia.org/wiki/Phabricator_för_föreningen (please observe that the document will be updated in a month to better reflect how the staff practically work on Phabricator)

For the weekly planing for all projects I am also involved in my role as COO. I currently do not see a need to add Product Owners into the mix.