Tested in CFME 5.9.4.2.20180802030318_f91df08
I configured two CFME regions, with Appliance A as global, and Appliance B as remote replication partners.
I configured LDAP auth with an AD server and SAM Account Name user type, on both Appliance A and Appliance B.
I configured a catalog item and catalog to order through service requests.
This service order was successful while logged in as an AD SAM account user on both Appliance A and Appliance B, a cross-region service order as described in the original BZ comment.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHSA-2018:2561