Sfenjy wroteI think its about 100mb per 1h and a half or two,depends on the activity in the server. If you are worried about that and have free time I suggest you join a US server and play at night when data usage is free.
Wouldn't that cause him latency issues? i don't know about planetside, but any game i tried on a US servers got ruined by 200ms+ when it was 60ms on EU servers. Haven't gotten the time to try this one yet, it's still on my to do list.