AppleTalk Remote Access does not have the ability to turn on power to a remote Macintosh.
There are third-party "wake up" products you can use in conjunction with AppleTalk Remote Access. After you wake up the Macintosh with one of these products, you can call back the remote Macintosh and connect in the normal fashion with AppleTalk Remote Access. Sophisticated Circuits offers such a remote "wake up" product called PowerKey Remote.