As someone already said, it boils down to what you define as tonality. I would personally include anything that gravitates toward a central axis. Therefore, traditional tonal music would be included, as would modal music. Any music based on mathematical algorithms, on the other hand, is a good example of something that will likely be atonal. Also, anything to do with set theory is atonal.
Coming back to the original question, good contemporary composers have a very diverse harmonic language and are quite versatile in that they can effectively write in many styles and combine several harmonic languages in an artistic way. So, yes, modern music employs both tonal and atonal systems.