All Subscriptions are stored just like other queues, in the JBM_PostOffice table. So if you have a topic with 5 durable subscribers, then you will have 5 queues that are stored in the JBM post office table. The name of the queue will be the client id. For instance, I set my client id as Jay for one of my durable subscriptions. The queue created for that subscription is Jay.SubscriptionName . When a message is sent to the topic, the message is then put into each one of the subscription queues.
Hope this helps.
If I were to create two subscriptions then
Sports/Baskteball and Sports/*
JBM is not going to do anything different if I were to create subscriptions
Foo/bar and Foo/blah
Currently we don't implement Topic Hierarchies. We have slated that for a task in JBM 2.0.
So the answer to your question is yes.
There is no release date yet that I know of, for JBM 2.0, but I'm guessing that it will come out between the 1st and 2nd quarter of next year.