In order to XOG out Task Dependencies, tasks must have a task id on it.
XML Open Gateway Developer Guide
CA Clarity™ PPM
PRTask Schema Tag
This tag is part of the inbound schema mapping for the Project XOG object. PRTeam is populated when you staff a resource to a project.
This tag uses the PRTask table, which can have 0 to many records and where PRTask.prProjectID = PRJ_PROJECTS.prID.
The Task (PRTask) schema tag has the following attributes:
Optional. Defines the unique identifier for the task. Required, if referenced by Relation tag or as a sub-project.
Table and Column: PRTask.prExternalID