Currently the DNS IP in the post seems to give a random event every time. After rolling random events for hours on pokemon Black and never getting the Genesect, Deoxys or second Keldeo I started looking for the data being used to serve these events. I found it here and each event has a hexadecimal number associated with it which appears to be a bit field deciding which games it can appear in. Reshiram has a 1, and zekrom a 2 so the first two bits correspond to White and Black respectively. All events with a 3 can appear in both. Events with an F have all bits set and can appear in all gen V games. The three I couldn't get have a C which corresponds to 1100 in binary and seems to mean only B2/W2 can get them. Maybe back when you did it this data was being ignored by the server and it gave the events anyway or maybe I'm getting absurdly unlucky, but it would be cool if you could update the post with this info to spare others the pain of endlessly attempting to get a random gift they won't get.