Every deposit to Gox has an unique address, so what you are monitoring is the recieving ip;
72.52.5.67. Mtgox.com resides at Prolexic Technologies in Hollywood, FL, United States. So if you monitor the flags on the map on this location, you have a pretty good idea. You check the listing further down the page to see the amount deposited.
Someone should make a page with some graphs with deposits and withdraws from Gox over time, with an inbuilt alarm to wake you up when something happens!!!
I think you have overlooked something. There is no receiving IP. The IP's are just the first node that gets it. Then added to the block chain. There is no way to monitor transfers to mtgox without knowing their clients deposit addresses.
Your logic may be valid for outgoing transactions but that info is useless. Would just show how much was transferred out of mtgox.