When I took CAB-1 and CAB-1L units apart, the rubber buttons looked the same, although I did not examine them closely. The circuit board pads that the rubber buttons contact have a different pattern/size/complexity for the whistle button between CAB-1 and CAB-1L.
Also, what I think everyone is trying to suggest is that the hardware and firm ware is vastly different between the two generations of controllers. It's not about connections. It's about the PIC and its firmware - they are different and non-compatible.