There is a DXT1 which has a 1-bit alpha channel, but even if it exists the game won't use it. As far as the game is concerned the alpha version of DXT1 simply uses more memory than the non-alpha version (the alpha version being 4:1 compression, the non-alpha being 6:1 compression).
I just agree with Vasudan Admiral (from his first post), it looks like reflection from the env. Turn off env and see if it goes away. If not then we'll know pretty easily. If it does go away then it's likely just a problem with the specmap, which would just need to be tweaked to fix the reflection issues on those parts of the map.