You'll need to pass both the CPL Skill Test and the IR. If you want an multi-engine class rating then you'll have to pass a licensing skill test (LST) on a twin (unless you've got lots of twin hours already or unless you do the CPL test on a twin). The training for the CPL Skill Test and the twin LST (assuming you're twin qualified in the USA) will be at the discretion of the Flying Training Organisation you go to. Then you've got the 15 hours minimum before the IRT.