I haven't read the interview, but I recently stumbled across some information saying that the Horde/Alliance only will only apply to the PvP servers. On the PvE servers, you'll be able to create both a Horde and an Alliance character on the same server.
I'm not sure if this information has been posted anywhere on the forums before, but if it has, I haven't seen it and this seemed like an appropriate place to post said info.
Edit: Btw, this info was found on WoW Warcry, which I've always found to be fairly accurate.
Edited, Fri Sep 17 02:40:37 2004 by syntaxic