Yesterday in the department we talked about some cases where in a written, proctored exam in which the use of any technology was forbidden, some students handed in clearly AI generated solutions. So there is an indirect proof that technology (a hidden phone, smart glasses ?) was used.
If you are caught with a phone during the exam, the case is clear, but such an indirect proof may be legally challenged.
May be a fringe case, but it's clearly another challenge that universities face.