[masraum]

depends upon the receiving bank.

I'd say that the funds change hands nearly instantaneously once the transfer is made.

I think it's not uncommon for the bank that cashed/deposited the check to have a "hold period" on checks over some amount the first time or two they are deposited. I think the hold can be anywhere from a day to several days depending upon the bank.

Someone at bank B should be able to advise the person with the account at bank B how long the hold period is and what the factors are for hold periods.