This is history repeating itself.
Something like this happened in my company. We had about 150 people operating various kinds of technical equipment.
They were employed by a certain company, contractor to us,
which had, of course, submitted the lowest bid.
In 1978 or so the German authorities
discovered that no tax or anything else was being paid.
To cut a long story the matter ended up in the German labour
court which decided that we were the employer.
Somewhere in the whole affair the contracting company informed its people that...
"you are not employed by us and never have been".
The "employees" had been a bit silly, mostly sending their money out
of Germany, but via the banking system.
I believe that is was the bank which they all used which informed the authorities.
Europe was of course "Cowboy country" in the early days of the EU. The people employed were mostly from the UK.