TODAY
Currently (12 Feb 2015), none of the Chopard Mille Miglia chronograph watches contain an 'in-house' movement but the 3rd party movements are adjusted and decorated by Chopard.
Here is a quick identification guide to Mille Miglia chronographs in-the-field:
Mille Miglia watches with counters at 3, 6 and 9 o’clock have Dubois Depraz module on ETA 2894-2 movements (except the Mille Miglia Vintage model).
Mille Miglia watches with counters at 6, 9 and 12 o’clock are non-Chopard integrated chronographs.
Mille Miglia watches with chronograph and GMT function utilise the ETA 7754 movement.

Chopard Vintage Chronograph
The rare (250 pieces) Mille Miglia Vintage editions are of a design inspired by the 1950s - 1960s. The hand-wind, integrated chronograph movement is an original old stock Lemania 1874 with fine Chopard finishing, encased in a contemporary 41mm rose gold case.
Regards,
MTF