[chrishajer]

Yes, it’s been done:

https://bbpress.org/forums/topic/a-phpbb-to-bbpress-database-converter?replies=33

https://bbpress.org/forums/topic/the-result-of-phpbb2bbpress?replies=1

https://bbpress.org/forums/topic/importing-from-phpbb?replies=26

These are old posts, but yes, it can be done. You might need to make some modifications to the linked scripts to make them work with your version of phpBB and bbPress.

But, it can be done, yes.