To put this into perspective, China's high-speed rail project in Indonesia connecting Jakarta and Bandung (a distance of 143 km) at a speed of 350 km/h was completed in just four months at total cost of $7.3 billion.
This line has seen an impressive number of passengers, with approximately 2 million people utilizing the service.
Its by design. When the 10 freeway in downtown LA got damaged in a fire and it was speculated that repairs would take months to reopen the freeway (for perspective the freeway does through the heart of DTLA and connects a lot of vital areas of the city with rachother)
They had it fixed in 5 days with enough political pressure.
They could have a series of high speed public transit all over the state if they wanted to, its not a question of resources since Los Angeles and California as a whole is a very very wealthy and resource rich state.