I think I would have a genuinely hard time not messing with this or trying to ride it. Both which are objectively terrible ideas nonetheless it feels really tempting.
I wonder if it is CAN bus? I bet it is, maybe it even has an unsecured OBD port. It might be super easy to get into its computer. If this would let you turn off or change its wireless connection you could have full control. If nothing I am sure this would mess with the GPS map and get it to do some weird mowing.
If it does have an OBD port they make over the counter wifi and Bluetooth dongle. So all you would do is give it an unexpected obstacle, wait for it to pause and pop the dongle in.
Not sure on these larger industrial mowers, but the little WORX robot mower I have does have a programming port open for firmware updates. There's been some custom firmwares out there; no need for signed code or anything like that.
And then you have every right to sue the beejezus outta whoever unleashed a robot into public that has super fast spinning knives but no obstacle avoidance programming.