Hello. I am a homeowner here in Berkeley, and have been using Twitter for the past month or so, and I was impressed at how easily it is for me to stay up-to-date with things happening real-time. For example, there is a conference going on in SFO, and I just subscribe to the search term for that conference and I see real-time updates from everyone who is at the conference and using that code.
Another example of course is that during the Mumbai terrorist attacks, everyone used the term "#mumbai" in their messages, and anyone subscribing to that term could see upates in real time.
One of the worst problems in a disaster is lack of information and nobody knowing what's going on or what they should be doing. If a disaster occurs in Berkeley, it would be very nice to get real-time updates through Twitter.
In particular, I can see an "official" channel coming from your office and the City of Berkeley in general, with important information that you want to disseminate.
I can also see an "unofficial" channel where citizens can post messages, things like "fire on 4th and Hearst" or "looting going on near downtown BART, stay away" or "if anyone needs extra firewood I have some".
When I say a channel what I really mean is that when you post a message you use a certain tag like "#berk" or "#coberk" or something like that. Then those of us trying to keep in touch can subscribe to this term and get real-time updates, and post our own updates as well.
If you set this up, and then let people know ahead of time to make use of these channels, I think this could be a very good thing.
You might want to also set up an agreement with local cellular providers that in the case of emergency everybody should have access to their data services even if they're not paying subscribers, so they can engage in communication through the Internet using their cell phones.