I don't believe Formalhaut is a canon system...
Nor do I agree that any user-made campaigns should be counted as canon. As much as I enjoy Derelict and Inferno, they are fanon and shall always remain so, no matter how good the storyline and mission design.
Someone else mentioned Shivans "being born from subspace". Once again: specualtion. That is not canon.
Ok, on another topic: why would the Lucy fleet be rogue? In my opinion, the Shivans sent it to wipe out the Vasudans and Terrans, believing it would be enough. When they saw us next, during the Nebular conflict, they took us a bit more seriously, using more powerful and advanced equipment.
I do agree with most installations we've seen being temporary affairs... but I don't believe T-V space is surrounded on all sides by Shivans. Apparently, we are quite far away from any of their home systems, otherwise I think we'd've seen a more permanent base of some sort. I'll also point out that all Shivan attacks have been from the (for lack of a better term) "east" side of the nodemap. If they completely encircled us, they likely would have attacked from all sides right from the start, and we'd have been finished.