It is quite possible the taller 6-pin-crossarm poles were being upgraded to ten-pin ones in this image. Ma Bell and other pioneer phone companies here in New England started out with six-pin arms commencing in the mid to late 1880s. The earlier arms were held into their poles via two diagionally mounted lag screws, sometimes with crossarm braces.

By c.1910 these older lines were beginning to fall (almost literally) into despair. New lines consisting of 10-pin crossarms with new wire became the standard as seen during upgrades. Most likely insulators in reusable condition (such as the earlier CD 104 NET&T ones made in two part-molds...aka MLOD insulators) were placed upon the new lines along with other functional hardware.