In all current (F-series) BMW cars, firmware updates are performed by the dealer using TCP/IP over 100 megabit Ethernet wired through its OBD-II port.

Curiously, it assumes RFC3927 -- the car assigns itself an IP within 169.254.0.0/16 and the diagnostic computer (a Windows PC running some native but mostly Java-based software) does the same once DHCP fails.