Earlier quoted context omitted.
The DiRT drills include the simultaneous loss of whole offices, including the complete obliteration of the Bay Area. Participants are instructed to pretend that they've been eaten by zombies and not communicate with anyone in a remote office, and that's backed up (as described in the article) by cutting the network links to & from the Mountain View corporate office. Now, there may certainly be larger systemic effects…
What happens if Google goes down for a while? Is it really that bad? Yes, Gmail and Drive may cause all kinds of chaos but I think I can survive quite a while without the search engine and YouTube.
On the scale of devastation this article is describing, none of Google's servicing being obliterated really matters but I'm personally pretty glad Google is prepared for multiple, massive scale disasters to happen at once.