ForumNG: Subscribes list showing students from all tutor groups (OU bug 11401)

Forums where there is a grouping applied and students have subscribed to there
tutor group appear to have the following problem. If a tutor looks at the
subscribes list it is showing students from other tutor groups as well as there
own. Sam has see and comfirmed this problem.

And example of this is the Tutor group forum on E100-10E