The website for this initiative - https://waroadusagecharge.org/ - is sparse on details on how this is supposed to be implemented. They mostly want to use odometer readings: "In implementing an initial RUC program, require annual odometer readings of participating vehicles as the method of mileage reporting to determining RUC charges."
You need to submit proof of out-of-state miles traveled to get exemptions - but only once this replaces the gas tax or if you enroll to get the gas tax reimbursed.