Starting Quebec, you can now use the g_service_catalog API which is available in all environments, such as, Service Portal, Now Platform, Workspace, and Now® Mobile.

It's also not working on ATF, and I will have to report this to ServiceNow to fix.

https://developer.servicenow.com/dev.do#!/reference/api/rome/client/g_service_catalogClientAPI#g_service_catalog-getValue_S?navFilter=g_service_catalog