Hello memeco,
Thanks for contacting us! Unfortunately that level of customization does go beyond the scope of the forums. 🙁
Off the top of my head, I’m not even sure this is possible as the tribe_event cpt and whatever bbpress uses are inherently different.
Maybe (a GIANT maybe) you could use a save_post filter to auto create a bbpress post when an event is created? It would have to have a different slug, but it might work. Like if you called it event-name-discussion or something. I’m not sure this is very feasible though.
Sorry I couldn’t be more helpful. Good luck!
– Casey Driscoll