Hello there, I'm the author of this page: Tethering With Blackberry Pearl On Linux [Thibaut Colar's Home]
Which explains how to tether using barry & XMBlackberry (back then anyhow)
This is a bit obsolete and complicated, so i made a new tool which only goal is tethering with a Blackberry.
It's much easier to install since it's just a python script (few dependencies).
See here for Instructions: BBTether - Easy Tethering for Blackberry on Linux [Thibaut Colar's Home]
I only have a Pearl and tmobile so that's all I've tested it with so far, it's brand new so probably buggy, but I would love it if other people used it and gave me feedback so i can improve it.
Please let me know how it goes and success/failue stories at tcolar AT colar dot NET