Are people allowed to leave their car overnight at this commuter parking lot?

Yes and on the weekend too

Yes I've left my truck there for the weekend

I have called customer services, and they told me it is fine to leave the car in the parking lot as long as your tags and inspection are fine. they will remove the car after 30 days of parking. There is no need for special tags or fees, you can just leave the car. safe travel. :)

I have also done it when I took the GoBus to New York City.