SDK: VRCSDK-2019.06.21.13.53_Public
Unity: 2017.4.28f1
The above build of the SDK is missing several triggers from VRC_Trigger including:
OnStationEntered, OnStationExited & OnDataStorage
I created a new unity project to test and I still does not show those options. Here is a screenshot of the options given with the chair prefab.
Edit: OnStationEntered & OnStationExited do appear on objects that do not have stations.