Only if they sign in to PSN. The MAC address is only visible on the local LAN. Not over the Internet. Sony won't make any attempt to track the PS3 unless they are requested to do so by a law enforcement agency. You have to file a police report before Sony will do anything, and the police will have to contact Sony and request that it report the IP address of the PS3 if it appears online again. Sony can also ban the system from accessing PSN in the future. That won't get it back for you, but it might deter someone from buying a stolen PS3 in the future.
As I said, they won't do it for you, and they won't do it voluntarily to help you recover your PS3 no matter who asks. If a law enforcement agency subpoenas the information as part of an investigation, then Sony has no choice legally but to provide whatever it has the technical ability to provide; and it will do so. There is no point in you calling. Playstation customer support doesn't have access to the information, and isn't involved in the process. Even if they did, they wouldn't tell you anything. Your problem is convincing a law enforcement agency to formally investigate the theft; instead of just documenting it. Depending on where you live, that may or may not be realistic.