Once users have permissions to your data stages, you can facilitate collaboration by making those users watchers.
The watcher of a data stage is automatically notified via email whenever an annotation, comment, or attachment is made. To add a Watcher, select any data stage and then use the Watch menu available in the toolbar.
Individual users can be made into watchers, or groups of users can be made into watchers. Note however that groups are not the same thing as environment groups. Groups are primarily a tool used by administrators to ease the creation of environment groups, however, they can also be used by regular users when using the Watcher feature. Here, groups are used instead of environment groups because there may be users who are part of a environment groups that may not necessarily need to watch the given data stage. If this environment group is composed of groups you can then just select a section of it for watching.
For example, "Environment group 1" is made up of "Group A" and "Group B". Environment group 1 has permission to a dashboard. You could make Group B dashboard watchers, then when a comment is added or an annotation or attachment, all users in Group B are notified. Group A is not a watcher, so the users in this group are not notified.