It's not that easy to calculate, especially since the 1 billion is about GDP losses, not losses in ticket sales.

I'm also lazy, but I'm willing to bet that the company loses less than 400M. After all the billion is for total costs is alreay on the high end. There are estiomates for a round a third. The unions demands amount to some 10k in costs per member (that's not what they'd get in hourly wage increases, but what the changes would cost). The union has some 40k members. So we'd be talking about some extra 4 billion. I.e. they'd have to strike for months to make it worth it. Now, not all those members are active, but if they get too much the other (bigger) union will demand more and so on.

For the country it's a vastly different story. If this were paid for by taxes and increasing GDP were the goal you'd most definitley not budge even slightly on the union's main demand (shorter working hours) since there's already a shortage in that area, but there'd be much more generious offers regarding wages. I.e. something like not a cent more for anyone working under 37 hours, but 50% more for people working 40+.