They generally don't compare sides during an EMG. An EMG measures underlying nerve damage. A spread of CRPS to another extremity would not make a positive EMG in that newly affected extremity. CRPS is in your brain (though you feel it in other parts of your body), so it does not cause an abnormal EMG. You can have an underlying nerve injury that triggers your CRPS which if fixed (in theory) may help improve CRPS symptoms.

Best wishes tomorrow.