See https://freebusy.io/icalendar for an example of that feature.
This has been released for Pro accounts: https://www.notion.so/cozycal/External-Calendar-Subscriptions-73156c690ffc47e6ad52e20de2e8aaa1
Basically it provides a read only iCAL feed url that is a combined feed of all of my busy times (the sum of my selected source calendars in Cozy Cal). So that someone can subscribe to my feed (typically people that book me regularly - my ongoing clients) and this allows them see our availability calendar right inside their calendar program of choice.
I'm in huge support of this!