I'm on BES. If I delete a calendar invite, instead of accepting or declining it, the meeting will go on my calendar marked tentative. I consider this a safety feature, since it keeps you from losing the meeting info if you accidentally delete it. Declining the meeting will cause it to not be put on the calendar.
I'm on BES, if you're on BIS or not using Outlook, your results may be different.
Would love to be able to disable this - when using a shared Google Calendar, if you add an event to it, and the user is set up to receive notifications, they get an email with an .ics attachment.
BB then adds this .ics appointment to the users primary calendar, and then it ends up being a duplicate of the event already on the shared (Google) calendar.