No. According to the bbPress plugin Subscriptions documentation:
Subscribing to topics or forums allows users to receive email notifications of new posts.
When a user subscribes to a topic, they should receive a new email of any new replies in the topic.
When a user subscribes to a forum, they should receive a new email of new topics that were created in the forum.
So if you subscribe to a forum, you will hear about new topics created in that forum. But you will not hear about replies to a specific topic unless you subscribe to that topic.
When in doubt, simply go to the forum or topic you are interested in and check near the upper right. If there's a "Subscribe" link, then you're not subscribed. If there's an "Unsubscribe" link, then you are subscribed.