There's a lot to consider here. My thinking is they will perhaps take over the top carpark outside BB studios. It'd make sense for them to utilise the driveway access behind Buzzsaw and over the train line into the old studio entrance. The entrance driveway can be diverted down the side road used for exiting with some small modifications, diverting all traffic around that top section of carpark and allowing unfettered access from the carpark to the construction site without needing traffic control.
But right now, we're still expecting earthworks, and like with Rivals, the first objects to arrive were the mounting plates \ bolts \ miscellaneous stuff for the footerings*
I'd suggest until we see large scale track arrival, they don't need to be walling off large areas of prime carpark, and storing down the bottom of WWW puts them out of the way of most guests, for objects easily moved about with forklifts.