Remember that quest in fallout 3 where you look for the android that ran away? And maybe you talked to the railroad member that gave you the android component? Well the railroad is a group of 5 people bent on freeing androids from slavery and believe the androids deserve rights.
Also, in the new trailer, we see a railroad banner when the character is flying away and looking out. Why is there a railroad banner there anyway?
My theory is that since androids are created in Boston by the common wealth, there are more of them there instead of in the capital wasteland. So the railroad thought there will be more androids to save in Boston and they should move to Boston. Then they migrated and set up there head quarters in that state and started their mission to save all the androids.
Do you agree with this theory or do you have a better one?