Just a thought.... The utilities here list 800A at 120/240 single phase in their fault current tables. Sometimes it's available, sometimes not. The people I can talk to at the POCOs are not the people who do the final POCO design. It is not unusual for the POCO design to take 6 weeks or more, and that's after someone signs a contract with them. No one is willing for me to hold a design waiting for the POCO design.
On the other hand I've had plans where I went with two services because the total was over 600A turned down in plan check because someone at a POCO told the reviewer that the POCO could special order a transformer that was bigger than their standard maximum size.
One of the on-going problems in these forums is that we all seem to think everywhere in the country does things exactly the same way they are done wherever we live. Some places I work I can get answers from the POCO quickly and accurately. Some places I can't. Assuming the EE can always work things like this out in advance may not be a safe bet.