I've done it. It's not so hard actually
Here you can see what i did to create it... (You need the head repository version of ogre thou)
http://gitorious.org/polyclient/polyclient/blobs/master/include/WorldManager.hpp#line377

the corresponding shaders are referenced in the source code and can be found here: http://gitorious.org/polyclient/polyclient/trees/master/bin/Media/materials

Ker beat me to it. Hmm, is mip mapping work for you Ker? I had to manually load in mip maps from a DDS myself. Without doing so my textures are black for the lower mips.

http://pastebin.com/9Sr41z5J

It's a bit buggy because it assumes mips are the same from both. Not checking if one mip exceed the other.

I want to look into loading texture array DDS files directly.