Well I think the whole point was to do it without onsite access. If he could call the location to get the MAC then he could just ask them to go to whatismyip.com and that would tell him his IP. Not to say you don't have good ideas, but i think they are more long term then short term. With that said, you can find the Mac of the CPE under MCA in internet tools. But like you said, to use that you would need to call Cox, and if you did that, you could just as easily ask them to look at your modem and just see what IP it's giving out.
I think the whole point is the IP is hard for someone to find out unless they have access to the account or on site. I think this is very much on purpose, otherwise you could figure out someone else's IP and do a DDOS or port scan (to see if remote access is enabled) or other shenanigans. Not saying that is what is happening of course, just saying it could. At this point, its simply intellectual debate. I think the OP has been answered.
