well.. it's probably neither. I'm guessing it's a vinyl wrap or something. Real wood nor plastic would conduct electricity very well 
*edit - oh.. by plastic you probably meant a wrap.. yeah. It would be pretty sweet if it was real wood lined with brass or something.. we can dream
*edit - oh.. by plastic you probably meant a wrap.. yeah. It would be pretty sweet if it was real wood lined with brass or something.. we can dream