Can you point me to implementation experience and lessons learned from using reference IEPDs in the clearinghouse, especially the Incident Reporting IEPD?

There is no systematic effort to identify projects or jurisdictions using reference IEPDs, so it is not possible to point to specific projects or jurisdictions..
The N-DEx initiative at the FBI has examined the Incident Reporting IEPD as part of defining the IEPDs for N-DEx.  More information is available at http://www.fbi.gov/about-us/cjis/n-dex/ or email: ndex@leo.gov.