If configured properly, the router will respond to GNS after an ipx gns-response delay period if no local server respond to it. In case the router gives an answer to a GNS because no local server respond to it, it could be done on a round robin fashion (ipx gng-round-robin). It does not mean that you can live without all this traffic crossing your network.
There are several techniques you can use to minimize these broadcasts (like IPX watchdog-spoof, spx-spoof, changing the SAP updates interval on a link, creating static SAPs, etc.).
However, the best technique I have seen is to filter unnecessary traffic in their source. I.e. on the updates sent between Boston and Paris, the Boston router does not need to receive a print server SAP located Paris since, usually, no one from Boston would print something in Paris. Some places may need only a default route instead of running full RIP.