Trolley problem situations absolutely can arise; whether the system is programmed to recognise and consider them is entirely beside the point. All that matters is how the system actually behaves when tested.

But I do agree that I don't see such scenarios ever occurring in reality because computer controlled cars are not going to get themselves anywhere near a trolley situation. They'll put the brakes on long before a human would ever recognise the situation as catastrophic. Almost all unexpected emergency situations are straightforward: the correct response will be to brake hard; the consequences are not ethical but rather dictated by physics.

Swerving onto the footpath is an absurd option for countless reasons and cars shouldn't be allowed even if the algorithm is fairly sure the footpath is clear.

The closest plausible scenario to the trolley problem I can imagine actually occurring: "An unidentified object has fallen onto the road meters in front of me, and I am boxed in with cars to my immediate left right and rear so I can't swerve. Do I break hard and probably get rear ended or do I break soft and definitely crash into the unidentified object?"