The only way to spectate a full server would be if the BF2 engine had a dedicated "broadcast" function like other games such as Half-Life and its successors, which relay game play to a separate spectator server.
As far as I'm aware it doesn't and never will, unless there is a very enterprising modder out there.
Now if someone could figure out a way to stream Battlerecorder to another server.
It is not playing a movie of the round, it is actually replaying the round as it occurred when recorded within the Battlefield engine.
Hmmm...