I've been playing around and may have found a way to 'use' TBP under linux. If you have TB on your Linux computer, use your TBP profile by saying:
cd .mozilla-thunderbird/ rm -rf fej2039jfladfj.default ln -s /mnt/usb/ThunderbirdPortable/Data/profile fej2039jfladfj.default thunderbird
The same would work for Firefox, I suppose.
there is only one catch. Don't ever EVER E V E R logout without manually saying
If you do not say this, TB will leave lock files behind which will not allow you to access your profile in Linux and it will completely screw over a Windows install of TB.
Anyhow, I thought I'd share both the hack (for those whose computers don't have wine--and aren't allowed to)and the caveat (I almost lost data. Getting it back chewed up a weekend.)
[Moderator RM: Remember: <pre> not <code>. I fixed for you.]