i have to assume that this wouldn't happen until 2009. I know that the upcoming lexus LF-A will be available as a hybrid and it is rumored that the hybrid is faster then the petrol version at the nurburgring. It would be interesting to see them competing in with a prototype as well as with a GT. i have speculated that they would do this but its great to hear about it, even if the article was a little weak on details.
as for the noise, it still has a petrol engine and im sure it will be fairly loud. if mazda is serious about the Furai, there will be plenty of noise to go around.