Hi Mike,
The "old" West Sebago station had a siding, but I've never heard or seen anything that would tell me that the "new" one did.
I have not looked at the photo on a higher resolution, but I'm not sure that is a "switchstand". I'll admit it does sort of look like one. But it could also be the chance alignment of several different items, like a bush aligned with a more distant telegraph pole. The building size and shape also tends to look more like the depot building at West Sebago.
My understanding is that the South Bridgton station (now a house) was similar to the depots at Sandy Creek and Perleys Mills, which were reportedly both gone by the late 1920s. My guess is the photo was taken after 1930.
I could be wrong about any or all of this, but those are my thoughts and worth everything you paid for them.
Best Regards,
Glenn