Your words all make sense but your points don't.
First: trucking is NOT efficient. Railways are far more efficient for moving bulk goods.
Consistent grades are still grades and waste a ton of fuel that can't be recaptured - except with an EV and, to a lesser degree, a Hybrid.
A hybrid will improve efficiency vs ICE in local delivery/traffic but a full EV is still significantly more efficient.
Putting a hybrid drivetrain into a trailer is ridiculous for the vast majority of situations. There are about 3 semi-trailers for every semi-truck to start with so that's simply wasteful and expensive.. If you only using them for 'special' runs then you complicate logistics which gets expensive fast.
Substations catch fire? I mean, sure. So do fuel stations...which ironically to your point also don't operate without power. So yah, win for EV there.
The /best/ approach is to build out the rail system and leverage EV Semi's for what would then mostly be local/regional delivery.
We won't do that so the next-best approach is to continue building out EV Semi's while focusing on where their immediate strengths are - local and regional shipping. As that continues, the 'charger deserts' become less and less ... while technology evolves to support higher speed charging and more energy dense packs. The need for long-haul diesel diminishes.
These trailers are just a solution looking for a problem. I'm sure they'll find some niches, but just that. It probably makes more sense adding a diesel generator to an EV semi than adding batteries to a semi trailer...but I'm not about to math that out.