The A-IRB banks under Basel II that specialize in such activities - for example, processing securities and payments and acting as custodians - will experience increases in their regulatory capital requirements on those activities. Every day these entities transfer very large amounts of federal funds, act as custodians for massive quantities of securities, and dominate payments and securities transfer systems.
The separation principle implies that the policy interest rate is not employed to alleviate stresses in the financial system if upside risks to price stability prevail.