As you can see in the photo to the left, this internal document shows that TMO customers can use BBM on their Blackberry even if they don’t have a data plan. If you have a Blackberry already, and you don’t have data, the document also mentions that no action is needed. October 21st is when all this starts.
This is a good way to gain more Blackberry users, as BBM is the biggest draw. The setback for a lot of mobile companies is that they make you get a data plan if you buy a smartphone on a contract.