Earlier quoted context omitted.
What mac address restriction is there? One sets them up on their robot interface so things will actually route. You get the assigned mac and use that in your virt ip or bridge settings. Are we talking about something else?
The Robot interface thing is actually relatively new (some years). Before they introduced that, all your IP addresses (and maybe subnets, too?) were delivered to your physical MAC address, period. Wanted to use a VM? Maybe use proxy_arp or some 1:1 NAT. Bridging? Not possible.
I checked my emails. My initial server with them was provisioned at the end of 2009 and it's accompanied by my Robot details. I did have IP aliasing on this bare metal server which also needed the assigned mac from Robot.