Automate based on public google calendar (not owned by me)

Configuration
1

I want to create automations based on a public Google calendar owned by someone else. I’m not using the Google Calendar Integration add-on because I don’t need access to my own calendars, just this public calendar.

I got the direct calendar URL,
https://calendar.google.com/calendar/embed?src=<calendar ID copied from Google>
and in Chrome it loads the calendar correctly.

But when I tried accessing the calendar in HA using the CalDav method, the initialization errors out with:

caldav.lib.error.PropfindError: PropfindError at '405 Method Not Allowed

Is there a preferred way to read a public Google calendar in HA so I can act on events?

Thanks in advance!