As it could be interesting for some scenario to update the caller ID during a call, specially for directed call pickup, i've finally found those interesting informations inside the aastra admin manual.
This could be used with **xx call pickup, or *8 group call pickup, to send caller id informations before that the user decide to intercept the call.
Update Caller ID During a Call
It is possible for a proxy or call server to update the Caller ID information that
displays on the phone during a call, by modifying the SIP Contact header in the
200 OK message and/or in a re-INVITE message. The phone displays the
updated name and number information contained within the Contact header.
The following parameter allows the system administrator to enable or disable this
feature:
sip update callerid:
This parameter is configurable via the configuration files only.
