[RET48]

(At least) two cranes were in the plan all along. On a project like this, changes "on the fly" are seldom made. My guess is that the black (Cornell) crane is on top of the steel because it couldn't be located on the bathtub floor without interfering with erection of the steel. I may be wrong, but I suspect that it will be used to lift steel on the west side of the core and to lift concrete mix to the core itself. The red crane can be on the floor because it won't interfere with construction there. Remember that the design includes large, three-floor (?) atria on the east side of the core. My guess is that the red crane will be situated within the atria but close to their western edges.

Please note that I'm not an engineer or project manager. The above is just my theory!