The main thing would be that the bank would play a role called a “registration authority”. The bank doesn't have to have the data.
I think you've been briefed on tokenization. The data wouldn't have to be held by the bank; the bank could be the enabler of saying, “You are who you are, we know it, you've come into a bank, we trust you, you trust us, we've done a registration check.” It would be a function in support of setting up the online identity rather than holding the data.