Complex sentence: The F line fleet comprises mostly PCC cars bought second had from Philadelphia and New Jersey which are painted in liveries from cities around the world, as well as 1920s-vintage Peter Witt cars from Milan.
Split into simpler sentences: The F line fleet is comprised of mostly PCC cars bought second hand from Philadelphia and New Jersey. The cars are painted in liveries from cities around the world, as well as 1920s-vintage Peter Witt cars from Milan.