It could be?
It could be as there is a station in Pittsburgh (WPGH-TV), on Channel 53 (Fox affiliate) that pumps out 2340kW of power....there could be potential interference, and it does say according to the FCC Records that "site is in Canadian Border Zone".
This could explain why the CITY-DT transmitter is directional. One would hope that maybe City could move to another slot, or moreso in theory, chances are when the Analogue shutdown happens in Canada, they would move back to 57 where their Analogue signal currently is. Unfortunately we'll just have to wait until then.