[chrishajer]

This is an old post, but the concept still applies:

https://bbpress.org/forums/topic/title-tags#post-9045

bb_title is the function you need to override with a plugin, such as this one. To see what bb_title and bb_get_title do, take a look at bb-includes/template-functions.php starting around line 305 (in version 0.9.0.2).