Like The Broker said, your best source of information would be a Consulting Engineer of the type who does application planning. They not only know the physics of engineering, they also have their ear to the ground on what is the mood of the FCC and what might they change sometime soon.
End of disclaimer.
What follows is blue-sky guessing.
First, you didn't indicate whether you are talking AM or FM? The rules are completely different. AND, the laws of physics are completely different.
In FM there is either a space on the dial available in the community you want to serve, or there isn't. Moving something there is not the question. If it will fit there, you ask for rule-making to have the frequency assigned, and then the whole world can bid against you to see who gets the assignment.
I don't remember station moves in the old days like we saw during the "window"... was it three years or four years ago now. I guess in an effort to have some efficiency of personnel, the FCC only accepts applications for some events when they have a "window" for applications of that type. To move and AM station or get a new one, or to change frequency more than three channels from it's present dial location even though the station stays on the current property, you can ONLY apply during a WINDOW. Those are new enough that we don't know what the future holds, but it may be five years between windows for AM radio. FM windows have their own time and schedule different from AM.
Why move an AM? One reason is that the FCC no longer grants daytime only new stations. If you have a community where an AM frequency would work daytime only (it would fit on the dial without interference to neighboring stations) then you go and buy a daytime only AM somewhere else and what you do apparently is relocate it's "grandfathered in" status as a day-timer. It appears you can even change frequency in the process.
The other reason for moving a station rather than applying for a totally new station may be that you can avoid paying the auction price and taking a chance on losing the auction to someone else if you can move one. Someone else will have to speak to that issue as I don't understand that process at all.
(That assumes I understand any part of this message.
