Tuxedo supports the XA standard. Database vendors are responsible for creating and supporting the XA compliant libraries which connect and interact with the their databases.
I think you need to check with IBM if their CLI/OBDC library is completely XA compliant or if they guarantee that a transaction started using their XA compliant DB2 client library will
include, as part of the transaction, changes made by executions of the APIs provided by their CLI/ODBC client library.
Tuxedo supports any resource manager that adheres to the XA specification. We don't regularly certify against all known XA compliant resource managers as the list is large and the version combinations becomes huge. If the vendor claims support for XA, then we will support the RM. As for the specific entry in the Tuxedo RM file, that is essentially just a mechanism to tell Tuxedo how to build XA compatible servers with the associated RM's libraries.
Oracle Tuxedo Chief Architect