This script can be used to extract iCloud calendar URLs. As a prerequisite the calendars must be visible in your local Calendar.app or iCloud preference pane.
The calendar configuration is stored in ~/Library/Calendars
with sub folders for individual calendars.
Example output:
> icloud-calendars
/Users/myuser/Library/Calendars/XXXXXXXX-YYYY-ZZZZ-AAAA-BBBBBBBBBBBB.caldav/Info.plist