Hello Alex,
let me give you two brief options on the issue. I will try to come back with a more in depth answer later, though. (If no one beats me to it...)
a) the Workbook_SAP_Initialize Macro in your Workbooks can be executed manually or by an event. Additionally it can be run at a later point in time. It will still register the callbacks.
(e. g. Try to run the Workbook_SAP_Initialize macro via "Alt+F8" from your workbook, after enabling Macros in the popup dialog and work it out from there.)
b) I won't suggest a change to an "all macros allowed" group policy. But perhaps you would like to pitch the responsible IT crew the curveball of "signed vba code with code signing certificates and an 'allow signed macros' group policy".
Regards,
Werner