I've notice weird behavior with the Set-MailboxCalendarSettings command. Specifically, I'm setting the AllBookInPolicy to $false for a room resource. After I make this change, the Calendar Permissions for the resource change - the Default changes from 'Free/Busy time' to 'None'. Not sure why changing AllBookInPolicy should be changing the Calendar permissions. When I change AllBookInPolicy back to $true, the Celendar permissions change to 'Free/Busy time, subject, location' and not back to the 'Free/Busy time'.
So, if a resource has been restricted (AllBookInPolicy $false), then the resource is reconfigured (AllBookInPolicy $true), the view permission to the resource are more open than you may want.
Is this by design, or potentially a bug with the Set-MailboxCalendarSettings cmdlet?