It's strange that a probably widely discussed topic is so hard to find... I've been searching for the answer, but I didn't find it. Can I somehow copy existing phpBB data (users, posts, polls, ...) to the newBB forum. And if yes, how?

Some Statistics:
phpBB version: 2.0.17
Xoops version: I haven't installed it. I need to convert my forum, or else it doesn't make a lot of sense.
newBB version: whatever one is included in the XOOPS download.

Number of users: 37
Number of posts: 28684
Categories: 5
Boards: 15 (wich two of are moderators only, and relatively empty.)

I believe you can find a CBB (the replacement for newbb) conversion script at: http://www.xoopsforge.com

Does CBB have equal functionality as newBB?

CBB was developed by Phppp - who was one of the developers of Newbb2 ... it is a highly updated version of Newbb2.