is it possible with blender 2.8 to import a pose library from the same armature in a different scene or .blend file?
You can append a pose library (under Action). You can then add the poses via the Action Editor
Yes, this is the appropiate method, but it is not working on 2.8 as it is creating a 0 Non data block for the user. So if you do append, save-close; re-open the scene the library active on the list is the only one that remains.
bug reported for 2.8.