there is no subscription to groups.
if you want to send tweet on a group you just put the content followed by #<group>
eg: i want to send hi all to blrgtug, I can send
hi all #blrgtug
There is a new feature added recently called lists.
By popular demand, Twitter users can now organize users they follow (or users that they don’t) into groups, or “lists”. This article will help you get started with some lists basics and hopefully get you ready to make your own!
Before we get started, it should be noted that following a user is not a requirement to add someone to a list; if you want to add a user but not necessarily regularly follow them, lists allow you to do that.