Back when the original Chico KPAY-FM CP app was filed for they tried to claim Class C status since the transmitter was just into that region. FCC didn’t buy it. City of License not transmitter location.
I think the borderline between ZoneII/ZoneIA line is Los Molinos and Corning California. Precisely, Exit 636 Gyle Road is the divide line. As KMXI, it’s still below the 40th parallel lines. I don’t think because of COL is the issue, if you look at Louisville, KY majority of their FM’s COL is Louisville, KY or along Kentucky, but since their transmitter is located in Indiana. Their radio stations are Class B/B1 instead of Class C2/C3.
§73.210 Station classes.
(a) The rules applicable to a particular station, including minimum and maximum facilities requirements, are determined by its class. Possible class designations depend upon the zone in which the station’s transmitter is located, or proposed to be located.