well, client could actually send mac address to the server but that information should be irrelevant for them. If they do collect my mac and I find it out, how could they explain the reasons for that?
edit: what rosie wrote means that they cant find out mac address from my connection to them, but there is no guarantee that the actual poe application isn't sending the mac to the server. Im not sure if they can get in trouble for that if they do record mac