Bug 85506 [Import/Export] [Preferences] import preference wizard uses a "save" dialog.
I20050215-2300 The import preferences wizard provides a browse button to select the file you wish to import from. However, it creates a Save As dialog. When you select the file you wish to import you are greeted with a warning that the file will be overwritten. No such thing occurrs, and otherwise the import succeeds.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/wizards/preferences/WizardPreferencesExportPage1.java
FileOutputStream fos = null;
        try {
            if (transfers.length > 0) {
                try {
                    fos = new FileOutputStream(exportFile);
                } catch (FileNotFoundException e) {
                    WorkbenchPlugin.log(e.getMessage(), e);
                    return false;
                }
                IPreferencesService service = Platform.getPreferencesService();
                try {
                    service.exportPreferences(service.getRootNode(), transfers,
                            fos);
                } catch (CoreException e) {
                    WorkbenchPlugin.log(e.getMessage(), e);
                    return false;
                }
            }
        } finally {
            if (fos != null)
                try {
                    fos.close();
                } catch (IOException e) {
                    WorkbenchPlugin.log(e.getMessage(), e);
                }
        }
        return true;
    }
}