To get the position of the spheres in the world coordinate system, you don't want to use the pivot. Instead, it's easier to use convert() to convert from scope coordinates to the world coordinate system. For each sphere, you can convert the scope's origin (or the scope's center - whatever point you want) to world coordinates as follows:
convert(x, scope, world, pos, 0, 0, 0) // x coord in world coords
convert(y, scope, world, pos, 0, 0, 0) // y coord in world coords
convert(z, scope, world, pos, 0, 0, 0) // z coord in world coords
convert function—ArcGIS CityEngine Resources | Documentation