HR IDoc Problem with Change Pointers

BACKGROUND

Our current SAP setup includes separate HR and FI Systems. When master data is maintained in HR, this is picked up by the change pointers, and IDocs for message type HRMD_A are ALE'd to the FI System where they're posted. This works just fine.

We're now planning to implement a third party HR Master Data Management system that will send IDocs to the HR system. When these inbound IDocs are posted in the HR system, we also need this to trigger the creation of outbound IDocs to be sent to the FI System (as if the data had been manually created directly in the HR system).

THE PROBLEM

In my testing with tcode WE19, I'm able to successfully post IDocs in the HR System for HRMD_A06, but it doesn't trigger the creation of outbound IDocs (for the FI System). Running the change pointer program RBDMIDOC for message type HRMD_A doesn't pick up anything. (However, if I manually maintain HR data via PA30/PA40, these changes are picked up by program RBDMIDOC.)

Any suggestions would be greatly appreciated!