I appear to at least have compiz running, so I have install ccsm, run it and changed the setting. I'll let you know how I get on.
It's working for me, I did the (sleep 2 ; xterm) & test while Thunderbird had focus and while xterm popped up in front of the Thunderbird window it did not steal focus. This was with focus prevention set to "high"
However I cannot find any documentation as to what the various levels actually mean (i.e. what makes "high" different to "very high") except some forum posts that suggest that setting this to anything above "Normal" can break some apps that expect focus when they pop up a new window.