It makes calls to the bundled GB binary file.
Anyway, as far as I know, if you have CWM recovery in your kernel installation, your stock recovery will be wiped so it would be impossible to make calls to the stock recovery. (and vice versa if you have a stock kernel).
And on a double whammy note, whichever recovery you have, it makes calls to the installed kernel to do its wipes (hence the origins of the brick bug with affected kernels), so its irrelevant if you have stock recovery or CWM recovery.
Its the kernel you have, not the recovery program, that determines the brick bug. The recovery program is just the interface that causes the bug to occur.