The bottom line, which I have heard from day one, is that one should not expect the "government", federal, state or local, to come to your rescue, especially if the catastrophe is long term and widespread. If the response to Katrina is any indicator (and it was fairly localized)
I tend to agree.
For example, assuming there was a widespread major disaster and your agency had no capability of re-supply, how long would it take to exhaust critical supplies in your immediately accesible warehouse? (Remember, that "mutually supporting" agencies would be in the same/similiar situation.) The same can be said for any stockpiles of food and medicine that you have in at your house for your family.
How many emergency ppersonnel would remain on the job and for how long, versus taking care of their own family? One of my clients encountered that, when a tornado came through a trailer park and housing area several years ago. The security officers on duty left the plant, they did at least lock the gate, but they just left their post to go take care of their families. It was my understanding that several of the VFD personnel did the same.
Remember, blood runs thick, especially when it comes to family.