I know you can battle Black/White 1 with Black/White 2 but what happens if the black/white 2 user brings out a Black/White Kyurem or a Therian Form of the Gene Trio?
This question seems so racist...
I found this on another question. And I'll quote it's source when I find it.
It appears in it's front sprite Kyurem form in Black and White, whilst in Black 2 and White 2 it would only show the back sprite of Black/White Kyurem. Obviously, Black Kyurem, White Kyurem and Kyurem all have the same 'coding' or whatever, so that shows the sprites. Game Freak are smart people. ;)
Hope I helped! :)
This is the source. Not the other source.
I believe that you are just not permitted to use Kyurem-B/W or the therian forms since they aren't coded into Pokemon Black/White.
If a Black2/White2 user sends out one of these forms they immedietly revert to their original forms - however they keep the stats and abilities of the new form
Black/white kyurem will revert to normal though it will have the special moves ice burn,or freeze shock and the ability will remain