If I have a GUI tool which will eventually be querying the base tables and I want to ensure that the "DEFERRED" MQT will be used, and there's no way that the tool will issue a SET CURRENT REFRESH AGE ANY, how do I tell DB2 to use the MQT without going directly against the MQT table in the query?

Simplest answer would be to issue an update db cfg for "dbalias" using DFT_REFRESH_AGE ANY.
I think that another solution might be to update the workstation using the GUI in its db2cli.ini CurrentRefreshAge=ANY .