>>some tunnels running under the border between Egypt and the Gaza Strip have remained in use, and were in operation even during the fighting. Contrary to media reports, the Israeli air force apparently did not use more powerful bunker-busting bombs to destroy the tunnels, rather than regular explosives.<<
Since Israel is at peace (more or less) with Egypt I can see why Israel chose to not drop bunker busters on their border.
You, apparently, do not understand how "bunker busters" work. The "more powerful" description in the article is misleading. They do not carry massively larger explosive charges -- they penetrate deep into the soil/concrete -- then explode a modest warhead. The result is a vertical "fountain" of debris -- with near-zero collateral damage.
If you knew what you were seeing, you could observe them in action during the "shock and awe" phase -- across the river, near Saddam's palace(s)...