We don't have a dynamometer or computer simulations to replicate EPA procedure, but in our driving, the Cooper S provided no indication it was no longer rated at 38 mpg highway.
Cars.com's KickingTires Real World Tests MPG On The 2014 MCS
With all the kerfuffle over the EPA's required lowering of the mileage figures for the 2014 MINI Cooper S Cars.com's KickingTires Blog ran its own real world test. It concluded: