The Poles were working 60 hours a week for 3,000 francs a month on the Löwenstrasse train station, part of a two-billion-franc ($2.2-billion) rail expansion project in Switzerland’s largest city.
Instead of being paid properly, they were replaced by employees from another company, said Unia, which subsequently launched action to stop work at the station.
The union had complained last week about “wage dumping” at the site and blamed Zurich cantonal officials and Swiss Federal Railways (SBB) for turning a blind eye to what its contractors were doing.
Unia said the Poles were falsely hired as self-employed “independents” through a Winterthur company.
Two of the Polish workers were caught through an inspection last week and were ordered to return to Poland, without having been paid for 200 hours of work, the union claims.
The Löwenstrasse train station, 16 metres below the Zurich’s main train station, is part of a scheme to expand capacity for the regional rail network that is currently the largest suburban construction project in the country.
SBB was critical of the union action.
The rail operator believes that it has more than respected its legal and moral responsibilities in the project, an SBB spokesman told the ATS news agency.
Currently, 40 sub-contractors employing 500 workers on the Zurich rail project.
"Each of these businesses guaranteed us in writing that they respect legal work regulations," the SBB spokesman said.
UPDATE: Work resumed on the construction site on Thursday, October 24th after Unia reached an agreement with SBB and contractor Brandschutz AG for the back payment of the Polish workers.
A Zurich official said the contractor did not violate a law intended to prevent salary dumping because it came in after the company had already signed a deal with the rail operator, ATS reported.