It is open. I had a service done there over a month ago. Very very convenient to have up north. When you request a service appointment through the app it provides that location as an option. Note that Tesla/google maps actually lists it in the wrong place. It’s right off Weston north of highway 7 on the east side.
I am scheduled to pick up there Sept 19 - talking with the rep, they seem to just be getting up and running for deliveries as he talked about the car getting delivered to Toronto, then being transferred to Vaughan.