A colleague of mine asked me a question which sounded like a breeze but either I missed the easy solution (if you know of one please post a comment to this blog entry). However I came up with a total of three ways to determine what management pack a group was created in:
1) For a one-off group you can get this information by opening the group in the authoring pane, and then going to create an override – the override location will default to the same MP.
2) Open the monitoring pane, Discovered Inventory, change target type, select View all objects and search on “group”. The first field shows the group names and the second field shows the management pack it is stored within (shown below).
3) Export all unsealed management packs to XML and search the XML files for the name of the group.