To check a Pokemon's IVs in Black and White 2, you have to beat the Elite 4 first. Once you've beaten the game, he'll be in the Battle Subway and will check your Pokemon's IVs; just select the one you want to check.
For EVs, you must also beat the Elite 4. Again, once you've beaten the game, you can call Bianca on the Xtransceiver and select the "Check Effort" and then select the Pokemon you want to check. If it says the Pokemon has worked particularly hard on it's -- stat, it has 252 EVs.
Source: Lots of EV training in Black 2 for the PWT
EDIT: Here is what the IV judge can say depending on the IVs of the Pokemon https://bulbapedia.bulbagarden.net/wiki/Stats_judge
As for EVs, it's pretty simple;
If she says that the Pokemon can still work a little harder, none of it's EVs are at 252
If she says that the Pokemon can still work a little harder but it has worked particularly hard on it's ---- stat, then the mentioned stat has 252 EVs, but the Pokemon doesn't have 252 in another stat.
If she says that the Pokemon can still work a little harder but it has worked particularly hard on it's ---- and ---- stats, then the 2 mentioned stats have 252 EVs, but it still has room for 1-6 EVs in another stat.
If she says that the Pokemon has worked really hard on it's ---- and ---- stats, then the 2 mentioned stats have 252 EVs and another stat has 6 EVs.
If I missed one, let me know ;)
