Thanks for posting the photos, JRNYFRISCO. I don't have an answer on this for you, but I may be getting requalified on this territory again soon so I'll ask around at that point. Honestly, I'm thinking more along the lines of PTC than CTC based on the antenna and switch position indicators.
I take it you've photographed the south end of Frisco in the last photo? The north ends of the sidings have power switches and signals associated with them, though the signals do not grant authority in any way. Southbound trains on this territory back in Frisco days had priority over northbound trains, so northbound trains would take the sidings when a meet was scheduled and the caboose would line the south switch behind so the southbound train could proceed uninterrupted. Now trains of either direction are given permission to leave the switch in the reverse position and trains making a meet on the main are informed that they will find the south switch at (name of siding) in the reverse position.
The signals at the north ends of each siding are protected by distant signals about two miles either direction from the north end of each of the sidings. A train in the siding can activate the power switch by pulling up to the signal overlap circuit and pausing (or just rolling very slowly) to allow the switch to open automatically. Of course, you must have a track warrant to do this or you will have an authority violation. Dorchester can be an interesting siding to deal with since the middle is the high point and the track slopes down toward each end at somewhere near 1%. Doesn't sound like much but if you get the combination of a heavy train that barely fits in the siding and wet or frosty rail and it can be a nail biter.
The other place I can think of that had signals was the area south of Sherman where the old SP branches off to the south (if I remember correctly, it's called "Melissa Block"). There was a signal mast about a mile to the south of that point but I don't think it even had a signal head on it. Also there is an old signal shed filled with wires and electrical components right there at the switch at Melissa Block, but the shed was wide open and clearly not in use. I had to line my train at that switch once and while waiting there I looked inside the shed. Nothing but a lot of dilapidated junk, unfortunately.
Anyway, whatever they're doing, any improvements are welcome. The run between Sherman and Irving is a beating as it is now, last time I was on it anyway. It's hard to keep the rail in any kind of decent shape with all those heavy rock trains, so slow orders are the norm. Even if CTC is installed, I suspect we'll still be dealing with the bad rail unless some major upgrades to the track and roadbed are in order.