SOGoEnablePublicAccess makes it possible to access SOGo calendars without account on the server. This access is unconditional and does not seem to have any means to revoke the rights selectively.

An improvement would be to have token based access:
A set of rights is granted via an URL for a certain time (possibly without time constraint) and is connected to an unique token.
The granter decides, which information is made available, like details or privacy state, and when this should be possible, maybe with a start date and/or end date. In this time interval anonymous users can access the calendar via the given URL. The granter can revoke the rights at any time, thus keeping control of the access. With this mechanisms it's possible to share calendars more fine grained and secure.