> A good example is that when it was proposed that one should be able to transfer their account number to another bank (as telecoms have to do for phone numbers here in Finland at least), the bank lobbyists said this is technically impossible, which is of course ridiculous.

This comparison doesn't make a ton of sense. Of course you can transfer your phone number - every phone number is mandated to be unique across all carriers. Bank account numbers are entirely internal to each bank and made up based on various arbitrary factors. What if the bank you want to move to already has an account with the same number as your account at your existing bank? How would that work?