The IP will determine which of the 60 google’s DC will hit first, usually it is the closest one to your location. But not all the DC’s are updated at the same time. For instance what I am seeing for google’s results in my location today will be very different in say california.
This is how google directs traffic to avoid an overloads. This would suggest to me the Google DC the spam tool uses is the closest one to its server.
I could be wrong but it sounds reasonable.
greek39