My answer is NO, but I'm not 100% sure.
What you can do is control your iTunes music in your computer or in your AppleTV(if you had one) with the free app Remote. If you can live with that your computer is still on when listening, it's almost the same thing.
Maybe there is some other app out there that will let you stream your music in the iPod touch to the Apple Express, but I haven't found it yet. Or maybe we have to wait for an update from Apple.
One thing I haven't tried, is to use a bluetooth adapter attached to the music system and playing the music wirelessly through bluetooth from the iPod touch.
Owner of a Beomaster 2400-2 and a pair of Beovox 1001 speakers.
My other favourite brands are Apple, Philips and Infinity.