Musique Concrete was never really some 'underground scene' so probably not. It's more historical than current, and historically it was routed in academia and serious experimental music for the most part, as I understand it. Nowadays any attempts at whatever "Musique Concrete" even means in the year 2014 are likely to be released on all sorts of different noise/experimental labels alongside other styles. Possibly there there are some relatively dedicated labels I don't know about thought, i'd be interested to learn more too.