I believe the command is SetdesiredFov xx where xx is the setting. The thing with UT is that you must set it before you join a server. You can have it set to anything you want. What you can't do is change it while your in a game online. (Unless a server allows it) I have not found any servers that allow it.
I've goofed around with an alias offline, it went something like this.
SetDesiredFov 20|OnRelease SetDesiredFov 100, As Andri said, it allows you to zoom with any weapon. It was kind of fun picking off Snipers with the Enforcer...