Can Ambient light from a Skybox be updated in realtime?

Hi, I'm setting up a day / night cycle for my game and have encountered a problem. I am using the following shader to update my Skybox and it is working fantastically. However, the objects in the scene are not being updated with the new Skybox lighting. The lighting on the objects is only updated when the play mode starts. Any idea as to why the ambient lighting isn't updating?

Shader being used to update skybox from day to night:
http://wiki.unity3d.com/index.php?title=SkyboxBlended

 

It looks like DynamicGI.UpdateEnvironment() is not updating the default reflection source, I only get the desired effect if I place a reflection probe covering the entire scene and setting it to realtime/every frame.
Also, is it possible to tweak the ambient intensity (from skybox ambient source) be updated without needing to call UpdateEnvironment? I could do this placing a light probe group but seems like the ambient source received by the terrain (and only the terrain) does not get updated this way.