Add 'Out of Office' event to all users' calendars

[Jon H]

Is it possible to create an 'Out of Office' type event on all user calendars in the workspace using GAM? Most of our staff uses a third party calendar scheduling tool for external meetings that connects to their calendar. It references their availability and unless they set an OOO event or accept the global invite that was sent at the beginning of the year for all company Holidays, their calendars show as open. 
I am hoping I can circumvent relying on the user to accept a meeting and just set it all for them.

[Andrew Prevost]

I just came looking for this exact same answer.  Would love to know if this is possible too! 

I've been requisitioned with adding all our company holidays as OOO events to all our users calendars.