The California State Railroad Museum has a 3 to 4-rail draw on an outside approach to its turntable. There is a section of 3-rail track along the street in front of the replica CP station.
The Nevada State Railroad Museum has a strange setup that involves a stub switch that works as a 3-rail to 4-rail draw. I don't think I have a photo of it.
I did arrive at NSRM during one of the Museum's events to find a visiting 3' gauge locomotive and tender setting on the switch with the tender derailed. It was backing toward the table and a visitor from another Museum thought the switch was set wrong and threw it in front of the back-up movement. The rear tender truck went on the ground.
Brian Norden