You've made my point for me. The trains are not continuously worked on. They sit there waiting and waiting.
I think a truer statement would be "It takes SFMM an average of 15 weeks to rehab a train because they are slow, understaffed and don't have parts on hand."
I understand that the trains aren't simply sleds on wheels but there isn't tons and tons of sensors either. Its grasping at straws to try and use them to justify 15 weeks of rehab.
How many ppl are on the maintenance team? Would be cool if you could ask them how long it REALLY takes to rehab a train, in man hours.