Given Espee's efforts to prevent BART from taking over the 'Peninsula Railway' the need to raise cash after the asset stripping merger of the holding co's was a great victory for commuters between SF--SJ(and Gilroy).
As to installed base and backward compatible... BART is like the PATH and IRT in NYC as opposed to the IND/BMT. We will never reconfigure the narrow tunnel subways in NYC; we will never 'standardize' BART. Too much cost for marginal improvement.

We have other examples of obsolete choices which dog us--25hz AC on the NEC from PRR days shifts to 60hz AC in Queens for the ROW to Boston. Means every engine or EMU used between NY Penn and Boston must have extra electrical equipment on board. Dead weight, degrades performance, but not likely to be corrected in my lifetime.