I was wondering that myself.
Around here the response is not quite to the levels you guys have, but we are mainly residential. Most departments only have one ladder (and some have a second for backup, but its not normaly in service). But then we have the County mutual aid system here, so townships back each other up. NJ has a history of "home rule" we dont do things on an efficent county or state level, each town, for the most part, has its own fire, police, ambulance, buildings, courts, etc. Every so often they throw out the fact that our county has more fire appratus spread among all the town departments than exists in the entire NYC fire department.
Anyway, yeah, I though that was a kind of light response for somthing like a major them park, unless like you said they were staging offsite.
-dave