I haven't had a chance to review them, I'll do that later.
OK, I had a chance to read through the 2019 Interim California Code Cycle requirements that will take effect July 1, 2021 (and for which jurisdictions may elect to permit work currently).
The good news is that they've properly coordinated the CRC requirements and the CFC requirements. CFC 1206.1 "Scope" has a nice clear "Exception" stating that Energy Storage Systems (ESS) in Group R-3 and R-4 occupancies (that includes all single family homes) are subject only to 1206.11. And CFC 1206.11 is an almost exact copy of CRC R327. So once these rules are in force, no question that you can ignore the CFC and just look at CRC R327 (for a single family home).
The other good news is that there's no requirement for sprinklers in CRC R327, which answers the OP's question for this version of regulations. Also nothing about aluminum signs (but I haven't checked the Electrical Code).
As to the CRC R327 requirements, a summary of notable points:
R327.2 All ESS have to be listed under UL 9540 (Powerwalls are, check)
R327.3.1 Spacing of 3 feet between individual units is required, but the ridiculous "3 feet from walls" is gone. Large scale fire testing results by the manufacturer can allow a reduction in the 3 feet separation requirement (haven't looked at the details of this).
R327.4 Powerwalls may only be installed in (A) garages, detached accessory structures, outdoors 3 feet from windows and doors "directly entering the dwelling unit" and (B) enclosed finished utility closets, basements, storage or utility spaces (finish with 5/8" drywall if not currently finished).
R327.5 Individual ESS units are limited to 20 kWh (Powerwall are, check). Aggregate capacity is limited to 80 kWh in locations in the list (A) in the previous paragraph, or 40 kWh in the locations in list (B).
R327.7 Indoor locations with an ESS need to have a smoke alarm, or a heat detector if smoke alarms aren't listed for use in the location type. I understand this to be standard type alarms, nothing exotic.
R327.8 Bollards if subject to vehicle damage
And that's basically all the important parts.
Cheers, Wayne
P.S. Some further details:
R327.1 This section says that if the ESS is labeled "For use in residential dwelling units" then none of the rest of R327 applies. Apparently this is a category under UL 9540A (a supplementary standard to UL9540 on thermal runaway testing) allowed for ESS using batteries whose individual cells meet certain performance requirements on the UL 9540A cell level performance test. I don't know what the requirements are, and I don't know if Powerwalls (using NMC technology) are capable of meeting them. So my assumption is this isn't going to happen for Powerwalls
I speculate that LiFeP03 might have a better chance of meeting these requirements, and if they could, and the Enphase products still use LiFePO3 and could achieve the labeling "For use in residential dwelling units", that would be a reason to pay more for the Enphase products.
R327.5 Further thoughts: the intention may be to impose the limits above across all location types, but the way it is written the locations in list (A) are subdivided into 3 types, and one could argue that you could have 80 kWh in each of the 3 types.
Also, the limits may be exceeded if the installation complies with CFC "1206.1 through 1206.9," but 1206.1 is the section that says Group R-3 and R-4 occupancies are exempt from Section 1206. So as written one could argue that's a null requirement, and there is no ESS capacity limit. I expect the intention would be better conveyed with the wording "1206.2 through 1206.9".
