Hi Alessandro,
I have looked into the new functionality and I beleive it was actually added in the release of the CCM 6.x train (not 5.x)
Peer Firmware Sharing
The Peer Firmware Sharing feature adds support for image upgrade optimization for the Cisco Unified IP Phones. When enabled on a root IP phone, Peer Firmware Sharing designates the phone to make a request for an image file. This establishes a transfer hierarchy and transfers the firmware image file from the root IP phone, down to the other IP phones in the hierarchy.
Peer Firmware Sharing also allows for the designation of a remote logging machine, a Log Server, for debugging Peer Firmware Sharing firmware image update logs that are sent to the remote logging machine.
Peer Firmware Sharing remains disabled by default. To enable peer firmware sharing to upgrade firmware for a few phones, in Cisco Unified Communications Manager Administration,
choose Device > Phone > Add New. Then, from the Phone Configuration window, choose Peer Firmware Sharing from the Product Specific Configuration Layout section.
Supported Cisco Unified IP Phones (SCCP and SIP)
7971G-GE, 7970G, 7961G-GE, 7961G, 7941G-GE, 7941G, 7911G, 7906G
Supported Cisco Unified IP Phones (SCCP only)
7931G
BAT Considerations
To use Peer Firmware Sharing to upgrade firmware for many phones at once, set the Peer Firmware Sharing field in the Phone Template window of the BAT (Bulk Administration > Phones > Phone Template).
Release Notes for Cisco Unified Communications Manager Release 6.0(1)
http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/rel_notes/6_0_1/601cmrn.html#wp48049
You will see no mention of this feature here;
Release Notes for Cisco Unified CallManager Release 5.1(2b)
http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/rel_notes/5_1_2/512bcmrn_1.html
Hope this helps!
Rob
