If the station is already set up for Horizon, then yes, that adds considerably to the potential for BIL
Two things I don't know: (i) how much traffic there is between BIL
I guess there's some because, as you say, Frontier, in both it's forms has served it before.
(ii) what is the most popular "bigger city" for oflks who live in BIL
? Or even RNO
It occurs to me that I know very little about Billings, or Montana. I might do a bit of research.