Yes, that article is from 1839, when they were finding "indications of coal", but I think it turned out the actual seam was south of there (Mansfield/Taunton/etc. area and south into RI). I look forward to anything further you may find.
And yes, that South Shore has always been a bit of a mystery. I think the Southeast Expressway functioned as sort of a modern-day moat. As a youngster I recall daily reports of gridlock, chaos and mayhem, punctuated by an occasional attack by a runaway locomotive, being provided by Kevin O'Keefe and other traffic copter reporters. Not sure I ever got over that.