Susan,
Truck not getting from A to B - then the shelter won't have staff, or supplies

At least around here (NYC) they RARELY own an actual shelter!

Most times (let's say a big fire) they open a "reception center", sign you in, and transport you to a hotel that they have a contract with - and hand you vouchers for food/clothing etc

IF and when they have to open a shelter, the mostly likely place is a local High School, particularly if school is NOT in session - it has the advantage of lots of room, lots of bathrooms, small rooms where the can isolate folks if need be, a nurses office, and a lunch room

The thing is, they won't have ANY staff there, any gear - nothing. They will have to roll a truck and some staff vehicles from either City HQ or one of the sub HQs. Even if they can't get from shelter A to Shelter B - hopefully they can get from one of the centers to the shelter. And they are NOT adverse to sending staff to the local deli/supermarket (the one 'live' shelter I was at that actually had clients - that's how we handled it - there was only 2 clients, it was easier to go to the deli and buy them lunch than send a truck out with catered food)

Like I said - the staff that will open the shelter will probably have a basic setip with them - it's a rolling cabinet or 2 with enough stuff to get started