What is firewall code for multiple meters on one building?

I'm not sure what you are asking about. There is a "National Electrical Code" (NEC) and there is a "National Fire Code". These two documents are published by the National Fire Prevention Association.

With respect to meter placement, that is up to the Utility Company. Disconnects can be placed at any point along the line side of the service.

A "Firewall" under the NEC is defined as a wall that will not burn for about two hours.

So I ask you, is this a homework question or a real question?