I have just done a quick test with Kershan,
While he is set to normal he can unsubscribe to one of our header channels ("Games / Default Channels", "Groups" and "Private, Personal, Temporary Channels") and then "Subscribe to Channel Family" which then ticks all the sub-channels of that group and displays the people within it.
He gets the error: "<14:04:09>
insufficient client permissions (failed on i_channel_subscribe_power)
" This is due to the fact that I disabled anyone being able to subscribe to one of the aforementioned groups as they cannot be joined and used as a channel. I can change this but it is completely irrelevant to what you're trying to achieve.
Enya you're not currently online so I cannot determine if you are in the guest group or the Normal group on TS and so I cannot debug further. However the permissions for subscribe are exactly the same for both of these.