Yes, if the person hearing the sound has the exact same soundfile.
Maybe late, but you can change it in the server config file which alarms are allowed.
Go to the folder where you saved the server, then: config\IC2NuclearControl
Here you can change which alarms are allowed ( S:allowedAlarms=default,sci-fi add here the sounds that should be allowed
i just tried doing this both ways. and im getting no display on my server of the sound.
Custom sounds are client-side: only you can observe the modified files.
Go to the folder where you saved the server, then: config\IC2NuclearControl
Here you can change which alarms are allowed ( S:allowedAlarms=default,sci-fi add here the sounds that should be allowed
Thanks! Just what I was looking for.