From what I can see, the combined person/assignment form business events are currently disabled in 11i, and come available in R12, where Oracle has implemented code to specifically raise these business events in the business process APIs.  However, with TCA integration, you may want to investigate if you can make use of the following business events:

.

oracle.apps.ar.hz.Person.create

oracle.apps.ar.hz.Person.update

.

The following note provides a little more info on the subject:

.

In this Document
  Goal
  Solution

Applies to:

Oracle Human Resources - Version: 11.5.10.2
Information in this document applies to any platform.

Goal

Can one use seeded business event:oracle.apps.per.api.assignment.update_emp_asg_criteria to
trigger when an assignment is 'Updated' using form in 11i?

Solution

The event do fire when hr_assignment_api.update_emp_asg_criteria API is executed.

The combined Person and Assignment form PERWSHRG.fmb use legacy table handlers instead of API's for database interactions. Hence the business events doesn't work in 11i for assignment form. But the business events are made available in R12.

In 11i release code level, this is intended i.e. the Forms will not trigger the business event, but the API's will.

In R12, PERWSHRG.fmb is still using legacy table handlers itself, but have made the business events available for this particular case (via an Internal Unpublished Bug 4707757).