I work in the US but at my company, team lunch is always paid for. Not only the food, but the time we eat is paid time (for hourly employees.) Mandatory “fun” should be on the clock and paid for by the company.
Definitely not the case for every company here, of course. But personally, I’d refuse to attend if the company weren’t paying for it.
The goal is that they reopen with the same unionized employees, plus back pay. That would be a huge win for the union.