1,200 miles is more than enough range for a semi.
I hate to burst your bubble, but a lot of semis in NZ work 24 hours a day, especially ones owned by bigger transport companies (that would have the money to invest in EV).
Every fleet truck that does the "Turangi 500" at night is used locally during the day.
Even one that is a local semi during the day, often does a night shift to a distribution centre and back.
Often they only come off the road for a service.
Owner/drivers are *maybe* an exception to this (if they do Auck-Welly), but not usually... during the day they hire another driver. It's the only way to make the money to pay for a truck.