Here's a question someone with your level of knowledge might be able to answer....According to Scott Fybush, he can hear CFCO 630 from near Rochester, NY, all the way to central Indiana, the only station that does so. CFOS 560 can be heard Days in Western New York and in Northern Michigan.
WTMJ 620 IBOC sidebands limit CFCO 630 in Western and Northern Michigan.
CFCO's towers appear to be really tall. Exactly how tall is tough to gauge from the 401 Freeway, which is at least a mile away (to the south). To what extent would that help them to get out? Obviously the wide open spaces and good ground conductivity surrounding the site helps matters in and of themselves. Even when CFCO was only at 1kw night, I was impressed with their groundwave signal.