I don’t actually think it’s really purely de-icing equipment related.
During any sort of adverse weather, staff themselves are likely to be stranded at home, either becoase they cannot get to work, or because they have to stay home looking after children.
This has to be factored into operations, both in terms of staff to run the services (and I mean all services, not just flight crew…) and also the fact that many passengers themselves simply won’t turn up for the flight ( for the above reasons or because they just don’t want to travel under such circumstances).
BA tends to cancel its shorthaul network when these irregular ops occur; it’s not a great situation, but savvy travellers know to book bmi for Domestics when such a situation occurs. bmi’s smaller network means they are simply less affected by such events.
BA proactively cancels services well ahead of travel. This works to minimise much of the inconvenience we associate with irregular ops.
Being proactive with cancellations avoids people turning up and clogging up the terminals; this allows people to plan ahead and make alternative arrangements, but also can give the impression that services are cancelled long after the bad weather has dissipated.
You also mentioned the cost of not running the services; there is also a significant cost for actually running a service which becomes seriously delayed or has to divert. Costs associated with such situations (landing fees, refuelling, repositioning the aircraft, EU claims, insurance claims, extra overtime payments, accommodation and transport) can be considerable, and this should be factored into the mix.
As it happens, I do think BAA should invest modestly in one or two additional de-icing rigs for the whole airport, with a levy on all carriers.
But, as we saw in February, and again last week, once a serious snowfall occurs, no amount of de-icing of planes can compensate for stranded passengers, aviation staff or a snow-bound runway.