Have any of the Railroad Safehouses been identified other then:

1. Ticonderoga (Believe this is Deacon's or one of Deacon's Guardianships.)

2. Mercer (This one is the SS, Chosen randomly from an unobtained settlement).

3. Augusta (Kendel Hospital in Cambridge).

In my current game I found a safehouse marker on a Red Rocket outside of Quincy. I thought this would be Randolph but now I am not so sure. I am wondering if Griswold Safehouse is Monsignor Plaza, but I haven't found any marking outside. There is an entry from a raider (or presumed raider) named Griswold inside, but that is hardly definitive.

Thoughts?

Edited to update list of confirmed safehouses.

I keep getting quests from this Caretaker at Abernathy even though my Mercer is at Zimonja, so I'm not sure if Abernathy is another safehouse or if the Caretaker just went to the wrong settlement....

Is the Lantern symbol at Abernathy or OZ?

The Fast Travel Marker for Mercer Outpost? OZ, but I don't see anything in OZ which makes it any difference from the other settlements.

If you're on PC you can try moving him to OZ. Open console and click on Caretaker at Abernathy Farm. Enter command without Quotes "Moveto player" to ensure you got the right reference. If he moves to you, go ahead and fast travel to OZ and run the command in console again. Once he's at OZ if he tries traveling back to Abernathy then I have no advice. Probably just best to leave him there.