Last I checked PSO2 doesn't work under Wine or anything like that. However, it might be possible with a Virtual Machine using Xen (or maybe KVM?), as I hear it's possible for the virtual machine to access the host machine's hardware, achieving nearly native performance.
Here's a guide that claims showing how to do something like this, but with Fedora as the host. This guide is a little outdated though (it shows install instructions for Fedora 16) and it's a little unclear since it looks like he made a dual-boot of OS X and Fedora or something. So be cautious.
http://www.overclock.net/t/1205216/guid ... al-machineLong story short, unless Sega explicitly makes a Linux version don't count on it, as PSU was barely able to run on Linux.