From what I understood, Apple Maps EV routing is only available with some 2021 BMW models. Apple Maps/CarPlay needs access to can-bus to determine state of charge, plug types and max charging speeds; currently only the latest BMW (not the i3) and future Mustang-e will sport this capability. Apple does not want to maintain a database with vehicles and their possible plug types and speeds, and I don't blame them - the car could provide this info already.
Once Apple Maps gets access to that data, you can just instruct it to take you to your destination and it should automatically calculate when you need to stop for charging and for how long. It should also be able to re-route you through a new set of charging stations should you drive off into the wrong direction. Apple Maps routing is based on TomTom information, indeed; though the instructions are not the same as TomTom.
Since most manufacturers have limited transfer of information between the canbus and the infotaiment system (I guess security issues), it means that Apple needs to convince the manufacturers to change software, hence I doubt we'll see many older EV models capable of being able to run Apple Maps with EV routing.
In addition, I understood that Apple will be using OpenChargeMap data, which may not always contain correct information, or even well structured data. So it's gonna be a slightly better half-baked solution.