Edda,
http://wiki.esoui.com/Events#UI
EVENT_ACTION_LAYER_POPPED (luaindex layerIndex, luaindex activeLayerIndex)
EVENT_ACTION_LAYER_PUSHED (luaindex layerIndex, luaindex activeLayerIndex)
both are fired when anything is shown such inventories or menus.
If you need to hook a specific then you really need the ZO_ globals.
However your post tells me you are looking for the 2 mentioned above.
For your "fade" you have diferrenct animation controls which can be found here:
http://wiki.esoui.com/UI_XML