Hi,
Thanks for the interest in our plugins. I can answer your questions.
Facebook Importer works with the core version of the Events Calendar found for free on WordPress.org: https://wordpress.org/plugins/the-events-calendar/
It does not need Pro to work and is not included in Pro. That is typical for most of our add ons. It will list on the product page if it requires another premium plugn.
Pro only includes the features found on the Product Page and no other add ons.
Let me know if you have any follow up questions.
Thanks