Most likely you won't get an arming of the "TCAS BLUE" (no TA to 'trigger') - hence no FMA, hence - back to basics in a manner of speaking, and fly in accordance with either your company SOP's, or in absence - Airbus guidance material. The trigger for you as a crew member is the absence (or not) of the "TCAS BLUE" and this then makes the difference as to how you'll handle the event.