Ground loops occur when there is a difference in potential or a return path for a transient current. If the system is properly drained in at least one end (in the telecommunications room) any transient leaves via the bonding/earthing busbar and grid. As the metallic faceplate is not connected to earth, there would be no ground loop. If code is followed, even if it is connected to earth/ground, the potential by code is equalized through the telecommunication bonding busbar. For a whitepaper on this subject, please visit here.