Back in the closed beta, those little worm hole things used to be the way you moved between some sector blocks (not all, but a couple of them). I think there's one in Alpha Centauri Sector Block as well. As to what they do now? Nothing, really.
From what I have read, those things were part of Perceptual's map system and were supposed to be superhighways that allowed increased speed as you rode along them. I think they are simply vestigal graphics from Perceptual's concept is all.