Thanks, Ted. I am seeing a pattern - this is not something that is available. I got a couple responses on the DBUG forum, as well:
From David Porter:
Check out this website by Hoover treated products: https://www.frtw.com/?q=exteriorfirex
That web site says that when fire treated wood is exposed to the weather, it needs waterproof coating.
From Mark Wilhelm:
I don't think you'll find this. A firm I write specs for did a deep search, thinking they needed it for a high rise building. I don't believe they found it, because they never got me info to put in the spec. If you do find it, please let me know.
We will have to use fire resistant wood, and protect it from moisture.