Disable browse thread on print server so it will not notify other print servers of the existance of your printers:

Hive: HKEY_LOCAL_MACHINE
Key: System\CurrentControlSet\Control\Print
Name: DisableServerThread
Type: REG_DWORD
Value: 1

Related:
Q181734 - Windows NT Print Browsing Architecture.
Q131902 - Printer Browse Thread May Cause Extensive Network Traffic.