if you know vertex index, you can query which bones (joints) effect that vertex as below:
short[] indices = animated3D.getSkinData().getJointIndices(vertexIndex);
float[] weights = animated3D.getSkinData().getWeights(vertexIndex);
now, indices points which joints effect that vertex and weights points how much each joint effect that vertex*
accesing vertex index is another story. AFAIK there is no direct way of it. using a CollisionListener and retrieving polygons id's from CollisionEvent and reverse querying IVertexController.getPolygonIDs for each vertex for matching polygons may help. Egon may clarify this.
* SkinData was not exposed before, I've just added a method to Animated3D to get SkinData. so re-download Bones. also note, Animated3D.getSkinData() and SkinData.getXX() always returns a copy, so caching them makes sense.