I've been noticing this a bit, until just now when things really looked weird.
I've seen in the past, pirates seeming to be flying long distances without a phase line.
And in my current game, I've noticed one of the enemies seemingly amass a huge fleet with ships coming in from several directions with no apparent phase lines.
Not long ago, I saw a few ships seeming to be coming down from another solar system, in a ONE system game !
But just now, I actually had a fleet jump out of the system we'd just had a huge battle in, and they did not go out any of the 3 phase lines, but somewhere between 2 of them. wtf ? The ships, instead of being visible as they went out the line, just vanished.
Is this a bug, or is there an Artifact that bestows the ability to jump between any 2 planets you like ?