/ CHINESE TO BUILD POLISH ROADS....
New roads in Poland, or any EU country are built to a very well defined specification for quality of workmanship and materials. The Chinese contractor would have priced against this specification under competitive tender. The client, in this case is the Polish Government (unless it is a PPP/PFI), will be obligated under the same to inspect and verify every agreed interim stage of construction.
The Chinese contractor will be cheaper, largely because they will bring their own labour. Speaking from my own experience, quality of workmanship in China is ok, so long as it is properly supervised. Problems will always arise when unrealistic construction delivery programmes result in the employment of unsupervised inferior skilled workers.