Well, actually, as it seems to me, all the coordinate systems with groups are broken now. Just because they are not transformed.
Also, instead of just transforming CALayer for group element, we need some magic like:

```
for (CALayer *currentLayer in [layer sublayers]) {
   CGRect frame = currentLayer.frame;
   frame.origin.x -= mainRect.origin.x;
   frame.origin.y -= mainRect.origin.y;
   currentLayer.frame = frame;
}
```

They have a good explanation here: http://www.w3.org/TR/SVG/coords.html#EstablishingANewUserSpace
(pictures are really useful!)

It seems to render correctly, though (at least, until there's no transformed text). I will try to draw an example.