There isn't a single parameter in the API call you could pass to an invitation BCC in Outlook. What you can do though is make multiple invites for the same event by making API calls iteratively with the same meeting information that updates the attendee email each time. This will let you create calendar events for each invitee that prevent them from viewing the emails of other recipients. Any updates to the event will also need to made iteratively to ensure all invites are updated. If you are not a developer this can be done using Salepager which lets you create BCC Outlook calendar invitations.