When I called some time ago, you are allowed to leave your car there overnight on a one-off basis, but you may not use it as a parking space. In practice, I have seen cars parked multiple days before without issue. Just don't abuse it.
Not sure the regulation for park and ride, but I'm sure you are not suppose to. However I parked overnight few times when I travel to up states during weekends(fri to sat). I definitely don't recommend for long range parking.
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