Question

Like through global link or whatever its called? Also can you trade through the top of Pokemon Centers?

Answer 1

I don't know if you can battle via emulator or global link but... i know that you can trade through pokemon centers

detail: You Can trade through pokemon centers with the GTS or GTS Negotiations
You can also trade through IR (InfaRed) Connection when tapping IR on your C-Gear
you should point your DS at your friends DS when he/she also tapped the IR Button