Sooooo much snark, and so little interest into what BART actually runs on!
Originally, BART was a master stroke of digital integration in the 70's, and it's digital voices announcing the next trains were a thing of the future: An early accessibility feature before we even knew what those were, really.
The larger engineering lesson from that is you're probably better off making standard solutions work for your situation than custom solutions. The wider gauge solved(?) the stability problem, but at the cost of always needing custom rolling stock, but more importantly, making Bart build-out significantly more expensive and unable to take advantage of existing track. That hurts the viability of the Bart ecosystem.
For rapid transits, 5'6" (broad gauge) is pretty eccentric [0] and was so back in 1964 when it was chosen; almost all other US rapid transits use 1,435mm/4'8.5". 5'6" is also doubly weird choice since tunnel diameter was one factor/excuse nominally used to object to tunnelling north to Marin County. Also it means the maintenance and carriage work can't easily be moved elsewhere.
(It is the widest gauge in use of heavy-duty mainline railways in the world, but that's a separate thing).