I'm glad they offered you a loaner.
Ok, so cold snap was probably not the cause.
It sounds like the dealer is on the right track - other than the general "electrical system" error, all the other ones are related to ABS and wheel speed, I believe. Maybe they need to replace the wheel sensors for all wheels (maybe hubs, too) - could be there is a lose or damaged sensor wire? I would imagine they chose the right rear because of a diagnostic, so it seems odd the work didn't fix the issue. Best of luck.