[lockem]

Late? I believe the Giulia Q was one of the fist production cars with BBW.

According to wikipedia many hybrid and EVs have BBW, which has been used in production vehicles since 1998. The article is flagged as needing work, so I do not know if that information is reliable.

 

[lockem]

On braking technology there are way more scary schemes than brake by wire:

Since the 19th century Trains and large trucks have had air brakes. An air compressor generates compressed air and the brake actuator just operates a valve that controls the adding and removing of air pressure to the brakes. Hazards include the air compressor not being able to keep up with demand and water accumulation leading to the system freezing solid. Also, there is a large delay between operating the control and the brakes responding. This really is the pneumatic equivalent of brake by wire, with the only "back up" being the spring operated dead-man emergency brakes. At least operators of these things are required to test them daily.

Mid-size trailers often have electric brakes (no hydraulics). For emergency trailer braking, these have a battery back up system. Does anybody check that said battery has and will hold a charge?

 

[lockem]

No. If anything a BBW system requires more h/w because there is actually still a traditional hydraulic brake control in place as a backup in case BBW fails.

I'm not sure what you mean here. The system in your Alfa Giulia uses hydraulic actuation of the brakes. The BBW system is self contained in the "master cylinder" assembly and consists of pump(s) and solenoids to operate the hydraulics. There is also a back up master cylinder so that if the electronics fail you have non-power assisted "stand on it" braking available. Various press releases claim that the system weighs less than "traditional" power assist plus ABS.

I have no idea what comes in a Prius, only that a Wikipedia author claims that it had BBW nearly 20 years before Alfa.

Bicycles often have the real brake by wire system...