How often do you think they are going to be replacing tires? Even if they drove back-and-forth continuously on that route, which isn't possible, they would likely only need to replace the tires once, or maybe twice, a year. They would just schedule a tire change at any normal semi tire shop. (Or even one of the Tesla Service Centers that are equipped to handle Tesla Semis.) Tesla isn't likely to put a full blown Tesla Semi service center every ~400 miles along that route. (Or maybe they will put one in each major city along that route.)While some local Tesla technicians would take care of the charging and machanic work, like replacing tires.
More likely for fleets that they will have one "extra" truck available to rotate in when one needs to be taken out of service for maintenance. (Brakes, tires, etc.)