[RightWhale]

Bose-Einstein Condensates are exotic alright, but we don't have to use them to wonder about relativity inside non-vacuum conditions. The simple glass in your telescope lens allows light to pass right on through fairly easily, yet what kind of relativistic effects are going on inside there? You could shoot a nuclear particle into that region at over the speed of light in the medium until it collided with something. Light slows down instantly at the air-glass interface, but the alpha particle keeps on trucking, moving faster than light for a while. What happens to relativity there?

[apochromat]

What happens to relativity there?

I'll make an attempt at answering that, and you can correct me if you disagree. It seems that the non-uniformity of the medias involved is being made evident in such phenomena. In other words, the light-speed reduction defined for a medium is a macroscopic quantity based on averaged effects of all the atoms that make up the medium. Looking at it microscopically, the medium is a combination of vacuum and atoms, and light is normally induced by the atoms to meander about instead of taking the shortest path through the vacuum.