Another think that strikes me as I read Jeanette's quote above is that at which point in an emergency will an Urban Kit fail and items from a Wilderness kit rule? If electricity is out over a wide area and water is an issue, my thinking is that something more inclusive than a strictly urban kit (which implies civilization and conveniences like running water and electricity) may be necessary.

Parts of a wilderness kit (water filter) come to mind and may be critical survival items in a post disaster urban setting. The GHB in my truck kit has an MSR mini-works water filter.