First such trials - then known as parallel landing trials were in the 60s (I wrote a magazine article about the procedures). It was a no-go because of the unequal offering of traffic from north and south and the dreadful ground control problems. Staffing requirements were very high too so how they would do it now with much less staff I don't know! Maybe all the problems have been resolved.... but I'd still like a grandstand seat of GMC when it happens.