I've already seen these chargers multiple times while driving by, last time on June 26. They are in the outdoor parking, and seem to all have attached cables.
I think the setup is still as visible in the Google Street View images from August 2024. The last 6 parking spaces on that row are equipped with chargers, but are not painted anything special.
On Google Street view, we see there are no gates, the parking is freely accessible, just access forbidden to everyone except Swiss Tennis visitors.