What is the ruling on working in Islamic banks that deal with the usurious Central Bank?

Islamic banks' dealings with the the central bank do not involve usury (riba), and deposits there do not accrue interest. The relationship of these banks with the central bank is limited to Sharia-compliant aspects such as auditing and oversight. Dealing with it is obligatory, so the one dealing with it is considered to be in a state of necessity, as long as it neither gives nor takes usury, nor aids in it.