Air Carrier departure from a foreign airport was cleared to 'line up and wait' only to discover TCAS displayed NORDO landing traffic closing rapidly; the landing traffic eventually going around approximately 150 FT above.

Narrative

Runway 5R closed so all departures and arrivals on 5L. We were told to line up and wait 5L. As we got onto runway there was a stuck microphone on an aircraft; Spanish was heard in conversation. As we sat in position; we realized via TCAS that an arrival was closing in for 5L. Unable to communicate with Tower; I told First Officer to try secondary Tower frequency...no joy; then Ground they simply stated they were aware. I thought about clearing the runway but it would have required moving a considerable distance toward the touchdown zone which I thought could be more hazardous. I thought it safer to stay put and hope the aircraft remained on glide slope and should pass 100-200 FT above us. From past experience; this Tower does not give landing clearance until runway is clear; unlike in the U.S. We watched as the TCAS counted down the arrival's altitude; +400; +300; +200; +100; still with the stuck microphone. Then; suddenly the aircraft passed approximately 150 FT above us in a go-around. We do not know if he saw us or realized they had no landing clearance. Either way; the potential for a catastrophe was high. Within 15 seconds of the go-around the frequency cleared and shortly after we were cleared for take-off. Now imagine this situation occurred in the U.S. where landing clearances are given with aircraft on the runway; and on a runway without a displaced threshold; in low IFR weather conditions. ATC rules should be changed. Perhaps the lack of a landing clearance could save the day.