Newer equipment can sometimes be re-purposed but older equipment often can't. For example older amplifiers would amplify the specific carrier frequencies used for NTSC rather than the entire 6MHz band used for ATSC.
OK - but I guess in any case they would consult with the OEM as he/she will need to assist with the assessment and/or supply services and/or upgrade components. I guess that NTSC uses a lower visual bandwidth 5.5Mhz as the stations invariably use separate sound transmitters on a dedicated portion of the channel feeding the same antenna through a combiner.
The trend is away from VHF-LO (channels 2-6). Since VHF-HI is already pretty much full, UHF is typically the only place they can go.
But surely UHF is the preferred spot due to probable future cell phone reception and other new technologies? Sure VHF-LO is finished. In the UK both VHF LO and HI are no longer used for TV broadcast purposes (since 1985) - way ahead of their time, wot?
Wonder what the network policy of CBC is in this regard?