I'm familiar with BA winter operations into Helsinki, Finland, and St Petersburg, Russia. Turnround done by handling agents at both places. Snow on runway (but adequately ploughed by airport and fully operational). De-icing turns up on time, baggage handlers ready, departures on time in falling snow, which of course the aircraft is fully certified to do. In fact sometimes even in these conditions they can pick up some of the time on turnround lost by the outbound at Heathrow !
Back at Heathrow in much better conditions it all falls apart.