It has everything GB has and much more. GB, remember, is a BEGINNER, NOVICE piece of software. All of those things are presets. Presets, especially in GB, take multiple effects processors, set them to preset settings, and from there you get your "mouse voice" and "megaphone" effects. There's not an actual megaphone plugin. They are making the sound out of basic effects settings within multiple processors.
When you get up to Logic, they are assuming you can probably figure out how to make a megaphone effect if you are up to using Logic, therefore, generic presets are there more for single effects processors. Of course, there are the channel strip settings. Those are like garageband's presets. Logic is just more customizable than garageband.
An easy way to make a megaphone setting is to turn on the channel EQ, cut out all the lows up to like. . . 500 Hz or so, then add some kind of delay. Voila, megaphone. Mess w/ the low cut in the channel EQ to get the megaphone sound you want.