As pp have said, it is unusual in the public sector. My understanding, though please correct me if wrong, is that as well as subsidised food, they can also claim back what they've have paid for the lunch.
I am angry today, angrier than usual at Parliament. My mp is a good egg but even he claims for £5000 train ticket a year (we are within an hour of london), how is that fair when NHS workers (and other sectors) on 25% of his wage have to pay for parking? How is it fair that an mp in a county over claims £2500 a month for a flat in London when he is a 45 minute commute by train away from Parliament?
And now they're taking food from vulnerable children, or as another poster said, their parents at least, whilst gorging on steak. Its painful.