Good evening Mark and welcome to the Events Calendar forum!
Thank you for your interest in our products.
We’ll be glad to answer your questions.
I would like to populate the same calendar to all my “Event Calendar” pages across these subsites.
This very feature will actually make it to our plugins this spring.
Unfortunately, I cannot commit to a release date at this point. But stay tuned!
Our blog posts and twitter feeds should keep you in the know 🙂
In the meantime, the only way to do this is to use the indirect approach: use something such as Google Calendar or iCal as a master.
Once that is done, you can simply use our Event Aggregator tool to populate your various calendars: https://theeventscalendar.com/product/event-aggregator/
I wish I had a better answer for you, but for now it’s the best one I have.
Best regards,
Geoff B.