The news today mentioned a sinkhole forming by the Acme Pond dam, and looking at the area on Google Maps it suddenly dawned on me the old "road" through the woods between the Acme and Whetstone Mills was most likely the trolley, as well as the causeway that crosses the pond between Acme and Bog Meadow Ponds:
This routing help shave the peak elevation of the line compared to having it run over present day Route 101. As it was they trolley operated with reduced capacity from Elmville (Route 12) to it's highest point here in East Killingly due to elevation gain the line had to make combined the voltage drop from their generators located in Rockland, RI (now under the Scituate Reservoir).
I believe the structure north of Bear Hill Road along Bog Meadow Pond is not the trolley line, but instead a dam to form another pond to the southwest of Bog Meadow Pond. I believe the trolley ran over Bear Hill & East Killingly Roads to present day RI Route 94 where it headed south to Foster Center (and on to Providence).