It isn't going to help unless the other jet has it too.
Not true. If the other ac has a transponder squawking regular Mode C, TCAS will still provide a TA/RA. The only difference is that it will not be a 2-way process, so the other traffic may be doing the same as you.
Having been attacked by Hawks ivo St Rumble and F-18s in the circuit (an RA on finals for an 'against the flow' circling approach is always fun!), I can vouch for this.
