[krishna.chari]

Just thought this will be helpful to others who are trying to integrate as well. Oracle Consulting suggested this solution which seems a lot cleaner for my purposes.
Set up an agent in OTM that will listen for changes to a fields on the order release. Eg: External status or ref number identifier of the Order Release. The agent will pick up values such as UNASSIGNED etc. When this value is set, the agent can unassign the order release frm the associated shipment.
From BPEL, update the Order Release, setting the status/ref number to "UNASSIGN" or some other user-configured value.
This seems to be a cleaner approach from an external program point of view.
Hope this is helpful.
Krishna