The question of "where is the border?" matters only insofar as it determines wether (or not) the Lebanese troops were entitled to fire warning shots. It is a quite separate issue to question the IDF response of firing tank shells and shooting missiles at Lebanese Army vehicles. Or, put another way: if the fence is a dozen yards INSIDE Israel then (a) Israel is justified in demanding an apology from Lebanon, but (b) the IDF was not "justified" using shoot-to-kill force in response to shots fired into the air.
Iraqi police fire tear gas as thousands of protests burst into Green Zone, storm Parliament (AP)
from the article: 3 Lebanese soldiers, journalist killed in clash on Israel-Lebanon border