Unfortunately, if a piece of content is moved from the user container to a place container, the email notifications for place following (also known as "Email Watches") will not trigger. To trigger an email alert, you could try @mentioning the group either by posting a reply to the comment thread or by editing the original content and adding the @mention here. This should alert to the inbox or email streams as per each following user's email follow configuration.
In summary, when you @mention a group, users following that group will receive notifications from within that piece of content. This is a quick and easy way to share content.
Let me know if you have any other questions on this.
Thank you, Jeph.