The rules do not mention it, the assumption is probably that expansion will be played with experienced rules anyway. But of course the expansion can be played with family rules as well; in that case you have no vehicle to pick the ladders up. I offer 2 solutions:
- Play without ladders, so the only rule changes from the basic game are windows and stairs.
- Stack all ladder tokens on one engine parking lot of your choice. You can pick them up from either space of that parking lot.
You could always simplify it even more and allow a ladder to be setup in any space outside the building without "picking one up" anywhere. Just go to the space you want to set one up in and set it up. Why bother with picking it up?