Well...atleast Vtis of 7th generation have immobilizers in them but not sure about exi...it may have or not....
the simple story is that the key is specifically designed, this key generates a binary code in ignition switch which goes to ECU which allows fuel system to work on....if any other key goes inside the ignition point ECU dont get that specific binary code and wont permit the fuel system to work...hence ur car wont start....also the cars with immobilizers can't be started through "HOT WIRING".....