I can confirm that the first section of the line to be converted to CTC was between the B&O (BR&P) crossing at MACHIAS and Ebenezer Yard at Buffalo. This was handled by the operator at MACHIAS because of the requirement in those times for an operator when two railroads were involved.
As an aside, PRR was interested in limited applications of CTC at a much earlier date than is often recognized, operating a substantial stretch of its St. Louis line immediately west of Indianapolis as single track under the control of the operator of the Monon crossing at LIMEDALE (near Greencastle) in a similar fashion, so the 1931 installation date is quite plausible.
The next step involved construction of a new one-story cinder-block KASE Tower in Sunbury, which controlled three sidings (FERRY, MILLER and BOYLES) between Rockville and Sunbury, and several interlockings serving the junctions between the Shamokin and Wilkes-Barre Branches plus Northumberland Yard. This was completed around 1958. FIDLER Tower, near BOYLES, was closed at this time, but the grade crossing of the Reading at SF Tower in Sunbury continued as a manned interlocking, with the Reading furnishing the operators.
At one time, plans called for the Wilkes-Barre Branch to be controlled from KASE, but PRR reportedly took exception to the price, and the right side of the USS board at KASE was never used.
Around 1959, another phase of the operation began, with another one-story cinder-block structure at NEWBERRY, which was actually located on the old Williamsport line. New sidings were installed at FAIR and MUNCY, the old passenger line through Wiilamsport was truncated and the two daily passenger moves in each direction backed into Williamsport. PINE and RICH interlockings near McElhattan were also incorporated into the system at this time. Towers at MONTANDON, ALLENS, LINDEN and RICH became casualties, but the Reading Crossing at MU in Milton remained manned and controlled several interlockings on the Reading via a GRS CTC board.
The remaining manned interlockings survived into the late 1960s, and were consolidated into a new board run from LYCO (as in Lycoming County) sometime around 1968-1969. I'm not sure when LYCO took over Newberry's functions. SF and MU were closed shortly after the Conrail consolidation, but KASE continued in operation somewhat longer before being incorporated with LYCO into a centralized system.
What a revoltin' development this is! (William Bendix)