I was not able to find anything concrete except the following, but it should be easy to test with wireshark. Connect 2 phones, attach PC with wireshark to the back of one of the phones, make a call between the phones and see if packets from the other phone arrive properly marked.
"•
When you enter the auto qos voip cisco-phone interface configuration command on a port at the edge of the network that is connected to a Cisco IP Phone, the switch enables the trusted boundary feature. The switch uses the Cisco Discovery Protocol (CDP) to detect the presence or absence of a Cisco IP Phone. When a Cisco IP Phone is detected, the ingress classification on the port is set to trust the QoS label received in the packet. The switch also uses policing to determine whether a packet is in or out of profile and to specify the action on the packet. If the packet does not have a DSCP value of 24, 26, or 46 or is out of profile, the switch changes the DSCP value to 0. When a Cisco IP Phone is absent, the ingress classification is set to not trust the QoS label in the packet. The switch configures ingress and egress queues on the port according to the settings in Table 2-2 and Table 2-3. The policing is applied to traffic matching the policy-map classification before the switch enables the trust boundary feature."
