All those are cars made by Sajmon14, the same author of
Bay City and
Eurocity add-ons. They're included in those add-on cities, so just download and play them to get also the vehicles. The yellow vehicle is called Airtrug and it's included in Bay City; that cop car should be included in
Sajmon's City. Those low polygons blue and green supercars seem to haven't been released.