GSX comes with a set of Jetway replacement .BGLs that are designed to replace jetways at all airports that comes with default Jetways.The Jetway replacement .BGL from FSDT will likely get an higher priority over other sceneries, so if you want to prevent GSX Jetways to show at 3rd party airports, the Config option in the FSDT Installer has a page that allows you to Exclude specific airports from the replacement set.