Alexis considers the question.
"I imagine that we could get blueprints from the office of planning, but I would doubt their accuracy. Paying off inspectors is cheap, and the advantages of not having accurate blueprints available is often worth it. We might find ourselves walking into a trap if we plan with them. The only way I can see to get accurate plans would be to sneak inside, and take a look around... which would sort of negate our current plans."