Hi @AndreaRose,
Could you please share a bit more about your Resource calendar and new public calendars?
If the login account of your Resource Calendar is an Office 365 account, you could use the event triggers or event actions of Office 365 Outlook connector. If the login account of your Resource Calendar is an Google account, you could use the event triggers or event actions of Google Calendar connector.
If you want to use event triggers within Microsoft Flow, you could type the "Calendar" key word in Search box, then all triggers related to Event would show up:
More details about Office 365 Outlook connector, please check the following article:
Office 365 Outlook connector
More details about Google Calendar connector, please check the following article:
Google Calendar connector
If you could provide more details about your scenario, we would provide a proper solution for you.
Best regards,
Kris