From what I have read, this functionality was released in July of 2016. I have Office 365 on a Surface Pro running Win10. I can share notebooks with others. They ARE able to see the content. They do not get notifications however.

Do all collaborators of a shared notebook need to be running a native verion of OneNote to get notifications, of should any and all collaborators get notifications with a notebook is updated by any listed collaborator.

(Does it matter if the collaborator has or does not have an MS-based email?)

Thx