I somehow doubt that the owner of the publish task is the problem.Are you using the same workflow in all these branches?If not - I'd suggest looking at the owner of the submittask in the workflow to see if it is using workarea_owner as the owner of the submittask. This is done in the OOTB workflows for workflows intended to be run by users in the Author role since they can't (or couldn't) actually perform the submit operation, but the workarea owner is supposed to have the role of Editor or higher and thus can perform the submit operation.
(dang - jbonifaci beat me - but I provide more details ;-) )
(whoops - that was suppose to be an Edit not a respond - sigh)