Have you considered using web services to exchange messages between the productions? This has the advantage of allowing the two productions to later be placed on separate instances.
If you want to do it through the mapped DB, you could write a custom business operation to store the records in a custom table which is mapped to from both namespaces and then write a custom business service that polls that table for new entries.
I have 2 productions A and B on the same IRIS instance sharing one operational database.
To be sure the two productions aren't conflicting with each other, I'm assuming that only custom tables/globals are mapped to the shared database and not any of the Ens* globals/tables/routines/packages.