Do you want the Mac address of the AMT device or the host computer? If it is the host computer, you can get the Mac address and NIC manufacturer name by running ipconfig /all command on a command window.
If it is the AMT device that you want the Mac address of, if you have DHCP enabled, the Mac address of AMT device is the same as that of the host computer, which can be retrieved using the ipconfig /all command. If you have static IP, you can find the MAC address of the AMT device by calling NetworkAdministrationService API from the remote system. Here is the format:
NetworkAdministration.exe -A -verbose -user admin -pass PASSWORD http://hostname:16992/NetworkAdministrationService
(You can find this exe from NetworkAdministration Sample in Intel AMT SDK)
If you want the Mac address of the AMT device in static IP mode from the client system itself, you can use the MEInfo tool that comes with Intel tools distribution. You have to work with the Intel contact for your company. You have to use the right version of MEInfo corresponding to your FW version
Let us know if you have further questions.