Another reason Henry is suggesting getting a pro in there, is that none of us have ever seen your building. A visual inspection would greatly factor into the design.
For one, since your building is 100 years old, the wiring was added most likely after it was built. Furthermore, it could have been replaced, whole or in parts, since then.
For another, this is certainly a permit-required project. You are going to need municipality approval, or at least you should. Moving main panels is very dangerous work, even for professionals.
And last, although you are correct about it being the utility’s responsibility for moving the wires, it will be your responsibility to pay for the work.
Assuming all this is worked out, the attic should you provide you easy rewiring for the second floor, which should result in a cost savings. Again, we have never seen your building.
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