How to get the lights positions from within a shader?

I asked this question before for Unity 2.x, but things changed with Unity 3 and I again cant figure out how to acess the lights and I dont want to use a surface shader in this case. I found the uniform _WorldSpaceLightPos0, but that would only be one light and what is even worse, is that it doesnt change when moving the light and not even if there is no light within the scene. This would for example be interesting for dynamic day-night changes within an iphone game.

Thanks for any help on this :)