My understanding is that it varies by temperature difference, but there's specialized series of heat pumps which work "okay" with very cold outside temperatures

My understanding is that it varies by temperature difference, but there's specialized series of heat pumps which work "okay" with very cold outside temperatures, even down to -25C, which are becoming popular to replace oil tank heating systems in Atlantic Canada. Apparently even when operating at -20C outside air they're still more efficient than electric baseboard heating. I don't know of any of the customers of the steam system in downtown Vancouver that use it for sterilization purposes, it connects almost exclusively large office towers. There's no hospital or medical facilities connected to it.