The host routing table tells the device how to make data connections to the blackberry network based on the mobile network the device is currently associated to. 310 is the Mobile Country Code (MCC) for the US. 410 is the Mobile Network Code (MNC) for Cingular. 260 is the MNC for T-Mobile, etc. So, most Cingular customers will use the 31041030 entry, etc.
It doesn't change for BES/BIS.
List of US MNCs: http://www.howardforums.com/showthread.php?t=657335
Cingular's entry points to 188.8.131.52 ports 19791:19790