Sounds like to me that you are talking about the "ignition switch assembly", not the ignition system per se. Right? If that is the case then you are right in saying that they are the same. Usually the only thing that fails in the ignition switch is the electrical portion of the switch.
As far as the key goes the Volvo dealer should have a simple hand operated key punch machine on hand. Unless things have changed since I worked in Volvo parts I used to bang out new keys all the time. You say you have the key code so if the dealer can't cut you a new ignition key then any competant locksmith should be able to make you one.

Regards, Jim