Yes, that MP 19 signal is totally inaccessible to railfans. There is a heavily wooded area on the west side of Groesbeck between the Parkway and 15 mile, and I think that CN may use a path through there to drive to it. Since your photos, the power switch machines have been installed at both North and South Mount. The switch heater is in place at SM (just needs the duct work), and the heater at NM should be in this coming week. Just a bit of wiring left in the plant, and I expect they will move on to the 21 Mile signal (sb approach to NM, and intermediate headed north). From there, it's on to Haven for the upgrade. PTC antenna and signal bases have been delivered to Richmond (MP 37) for the sb approach to Haven. Also, they have been busy in the Mt. Clemens area installing heavy duty electric lock switches required in CTC territory at the remaining customers. So, they are making tremendous progress, and perhaps we'll see more of it cutover in the coming weeks.
I've enjoyed tracking the signal locations and watching the work, as well. Thanks again for the pictures!