Are there any special conditions for encountering Lanius?

I have been playing a lot of FTL recently, all of sudden I'm drawn back into the game, and with a vengeance. Since I abandoned the game a long while ago, advanced edition was released, and so I'm playing with it enabled all the time now.

As far as I know, the advanced edition adds a whole new race - Lanius, though I wasn't reading up on them in the wiki on purpose to avoid spoilers. However, I can't find any "Lanius Secrors", "Lanius Homeworlds" or the like so far, and never heard of them in game. Am I just unlucky, or is there any special condition to finding them?

The lanius can be found rarely in any sector with advanced edition on, but their heedless advance in search of metal causes the original inhabitants to flee, leading to an "Abandoned Sector" with a much higher chance of encountering these ship eating locusts.