TURIN – BMW is stepping up relations with Bertone and Pininfarina, union officials here say, and could tap the Italian coachbuilders to design and assemble limited-series cars for its Mini, Rolls-Royce and BMW brands.

Bertone confirms it is working with the German auto maker on engineering two Mini derivatives for introduction in coming years, but the firm is not commenting on reports it also will participate in development of a limited-edition vehicle for Rolls.

Bertone has designed and produced limited-run models for BMW before, including the C2 2-wheeler and the 3200 CS coupe unveiled at the 1961 Frankfurt auto show.

Pininfarina isn’t commenting on reports it has been contracted by BMW to help build a prototype-series with a run of 144 vehicles. The Italian firm’s two German branches, Pininfarina Deutschland and MPX, have a long history of providing engineering assistance to BMW and building prototypes for the auto maker.

Pininfarina is well established in Germany, where it has facilities in Ingolstadt, Leonberg, Munich, Russelsheim and Stuttgart.

Reports also indicate Pininfarina is bidding on a contract with BMW to build 15,000 vehicles annually over a 10-year period. It is unclear which model would be involved, but a decision is expected to be announced soon.

Meanwhile, both Bertone and Pininfarina are in talks with BMW over the possible acquisition or lease of a former Pininfarina factory in Grugliasco, about five miles (9 km) from here, now available after a government-backed scheme to build De Tomaso vehicles there failed to come to fruition.

The facility now is controlled by the Piedmont Region Agency, and some 900 idled workers are hoping BMW chooses the plant for a production program with one of the two coachbuilders.