I have three G Suite accounts and a personal Google account, and until recently, there was little need for the Google Calendar to have any real use.
Now however the powers that be finally discovered the smart re-scheduler and the other Google tools for managing meetings and schedules; unfortunately I'm now in a position where I've got events notifications all over the place and because each of the calendars do not know about each other, I'm losing all of the advantages of rescheduler / free-busy status.
TL;DR, Four calendars, unified 'free/busy' status without having to manually copy every event please.