You can configure an alert to send notifications to all users in a group. This is done by selecting the "All users in [Group Name]" from the "Recipient(s)" option when adding/editing an alert.

Next, you need to assign users to the group. Although you can set group permissions to allow a user "Access to all groups" this will not make them a member of a group for alerting. You need to edit the user from the Users tab then select which groups you wish them to be a member of.