Pvp wlocks Alliance icecrown

So I'm new to the server and the Wotlk expansion, I'm a hard alliance member but i've read that pvp locks are impossible in alliance side due to undead having a racial that counters fear, so that any pvp lock should be in the horde, is this true? I know this applied in vanilla but i'm not sure if that still applies in this expansion, an answer would be greatly appreciated!

P.S - Incase it is that way, I'd rather class change then be horde, what mage spec is decent this expac for pvp?

Welcome.

Undeads have indeed a racial that breaks fear (will of forsaken) but it's nowhere near the level of gamebreaker that you mentioned, don't listen whoever told you so lol. It can be used basically once in a fight and you can fear them again.
There are some abilities against fear effects, from all classes, they can be annoying but you will always be able to do something through it.
So if you enjoy it go for an alliance warlock without problems or concerns.