BMW offer also includes specially equipped vehicles for state, diplomatic, security, authority, escort, protocol etc purposes.

Eg. police vehicles, fire brigade vehicles, security service vehicles, diplomatic / state protocol veicles etc.

And those 7ers are most likely diplomatic / state protocol vehicles - with LEDs incorporated in side mirrors (and usually also behind bars in kidney grille) which usally blink in blue color (or red if required, and have the same function as rotating / blinking blue lights on such vehicles.