That is quite an interesting situation you have there. I have few questions about your setup. On the AMT client through the OS, can you ping ProvisionServer.yourdomain.com? Is it possible that your DNS server is providing the IP address that is unreachable as the first IP address? May be you need to change your DNS server to provide the valid(reachable) IP address first or may be you need to bridge the two network interfaces on your ProvisionServer. I am very curious to see if the OS on AMT client can connect to your Provisioning server. Also can you connect or ping to AMT system from your ProvisionServer?
Let us know your findings.