When engine out, you select TA. This is not SOP as such but an action required by the checklist, written by the manufacturer. This means that if there is a potential conflict with another TCAS equipped aircraft, the one operating with the normal TA/RA selection will be issed with a the RA. Not doing so might mean that an "avoidance contract" might not be capable of execution for performance reasons - with unpleasant consequences.
PM