ATC and their voices come from FSX (or the addon in use), MCE just offers the interface interaction. But I haven't tried that feature as my ATC is online or totally silent when I just want to fly.

I think you folks will like MCE, that's where the trial comes in handy. You will also like the voices for the FO as they have nothing to do with the boring videos on the site. I've actually had to laugh more than once about my smart FO, telling me that my curse word on the approach was inappropriate behaviour for a Captain.  ;D

For the folks running a non English version of Windows, some preparation might be needed though.
But that's needed on all current voice titles for FSX, may this be FS2Crew, VoxATC or something else. They are all based on English voice recognition, which can be added for free (and legal!) to any Windows Vista/7 version. So be aware that this step may be the worst about that program.