I bumped into your blog while looking for info on that old railway line, very interesting. I lived in GPK from 64 to 66 when I was 10-12 yrs old, also lived in Mackayville as a very young pup. I have vague memories of the M&SC and the tracks behind Henderson's, so always wanted to know when they were decomissioned, I thought it was later, maybe 66 or 67, but know I know it was more like 1960. Thanks for the info. And I got excited when I saw the street signs in between the tracks, I thought there may be a fragment left somewhere but reading the rest of the blog I guess the shot was from where you live now? I lived at 422 Hubert, the only address past Third where it dead-ended in the field.
Let's see if we can get an answer for you.