This may have been answered in this thread already but I've looked around and can't find anything. Can someone tell me for sure how many times you can get the game specific legendaries (not the kami trio)? I'm assuming only once as GF never make anything easy but I was hoping that wasn't the case.

To explain, both my friend and I have the Dream Radar and I have HG and P whilst he has SS, D and Pl. So if I use P with my 3DS and get Palkia, could he then use P with his 3DS and get a Palkia on his game as well? Or would it lock him out? Is it one Pokemon per 3DS or per cartridge or if the 3DS and cartridge link or not? Any ideas?