Rav Zilbershtein was asked if the promise of the Chazon Ish extends to Modiin Ilit and other Haredi towns.

Rav Zilbershtein responded that while the Chazon Ish himself never said so about any place other than Bnei Braq, and he himself (ie Rav Zilbershtein) cannot stand in the place of the Chazon Ish to extend the promise, but it is clear that the promise was based on the Shabbos observance of the residents of Bnei Braq. Any place that observes the Shabbos - the promise and security applies equally to that place, and bombs will not fall there.

source: Hamechadesh

If it provides people some comfort and calmness, more power to him!

I would note, that there are plenty of towns across Israel that are fully shomer shabbos, and it isnt just limited to Bnei Braq and Modiin Ilit or even just to all haredi towns, though I would note that just this past Thursday a rocket landed and exploded in Beitar Ilit, a fully Haredi and shomer shabbos town, with several injured (thankfully nobody was killed). If Rav Zilbershtein is correct, they should all have this protection of the promise of the Chazon Ish, and I hope they all do.

I do wonder if the protection of the Chazon Ish promise requires the entire city to be shomer shabbos or can neighborhoods within a city get the promise applied as well if the entire city isnt necessarily shomer shabbos but some neighborhoods within area. I suspect it does. Even Bnei Braq isnt fully shomer shabbos, though today the bulk of it is. In the time of the Chazon Ish there was a significant portion that was not, such as the Pardes Katz neighborhood, among others. Even today, while Pardes Katz is more frum than it used to be, it still isnt fully Haredi.