You maybe will be interested in CBarge - Conference Barge. You will need Follows a short description:
Conference Barge and Privacy Feature Descriptions
The cBarge feature allows users with shared octal-lines on their phones to press
the cBargesoftkey to “barge in” and join a call in progress on that shared octal-line. When a third party joins the call, an AdHoc conference is created. Other users who also have cBarge configured for the same shared octal-line can join the
conference, up to the maximum number of participants.
Multi-party conferencing must be enabled before you can configure cBarge and Privacy. Conference Barge can only be configured on IP phones that have at least one octal-line shared extension.
For more info CCA 3.2.1 Admin guide p.403.
If you configure under CLI p.651of Cisco Unified Communications Manager Express System Administrator Guide (ed. 7 dec 2011).
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