The earliest mention of it in the Teamcenter Help files is for v10.1.2. It's listed under Managing Maintenance, Repair, and Overhaul Data -> Service Scheduler Guide -> Configuring Service Scheduler -> Configuring Service Scheduler workflows.
Here's the section where it mentions the preference:
Validate job card and job task reassignments
Job cards and job tasks can be assigned to a user in a specified discipline. When a workflow process is triggered on a job card or job task, the workflow task is assigned to that user. If that user attempts to reassign the workflow task and it has the AUTOSCHEDULING-person-reassign-validate handler attached, the task validates that the new user belongs to the discipline required by the job card or job task. If the new user does not, an error is displayed.
To configure the workflow with the handler:
Set the EPM_delegate_notification_handlers preference value to AUTOSCHEDULING-person-reassign-validate.
Create a workflow process template with a Review task.
Add the AUTOSCHEDULING-person-reassign-validate handler to the Start action of the perform-signoffs subtask of the Review task. There are no arguments to add to the handler.