I'll make a small tutorial how to use environment mapping with alpha channels. Should be finished in some minutes, maybe in some hours, maybe tomorrow (I've to go to school tomorrow, and it's 2:00 am :P)
But I'm sorry, as much as I know it's impossible to use a environment mapping shader + transparency + only some parts of the model are "shadered" at once.

p.s. The tutorial will be german, because my english isn't very good