At our company, the Captain may select TA when operating on closely spaced, non PRM approaches, when noted by company produced airport information pages, unit malfunction or directed by checklist.
When operating in TA (at least on our aircraft) the ND will only display nearby aircraft when a TA is generated, for the period of time the TA is active, after which it returns to not displaying any nearby aircraft.
Is this the experience of others reading this thread?