@nexxco great questions! If you're not familiar, the replacement cost coverage basically covers the gap in the unfortunate event that your vehicle gets written off during the coverage term. So let's say you're 2.5 years into ownership and paid a hypothetical $45,000 for the car brand new but it's now depreciated to a hypothetical value of say $30,000. If the vehicle is written off without the coverage, you would get a cheque for the depreciated value. With the replacement cost coverage, I believe you get a cheque for what it would cost to order the equivalent vehicle brand new again. If I remember correctly. To us, it was worth getting, but everyone's views on insurance will vary.
Tesla themselves (outside of California and soon some other US states) don't actually deal with insurance at all. However, you're not allowed to drive it off the lot without getting it registered and at least basic insurance, both of which are handled via ICBC. So like all car dealerships in BC, there is an insurance agent sitting around the dealership (or nearby and can be called in as needed) to help you. They do not work for Tesla and instead work for various 3rd party insurance broker companies like Westland and many others. They can all offer you ICBC products, and depending on their company's partnerships, they can offer you various 3rd party options for optional insurance. Hopefully that helps clarify that a bit? So they don't work for Tesla nor for ICBC but have to be there to help you register and insure during your pick up. Same at any other brand's dealerships as well in BC.
As to what happens if you sell part way through: you would have to ask. I believe you can transfer it onto your next vehicle, if I remember correctly--at least for our policy. Other providers might offer different options so definitely ask around.