Someone figured out how to optimize their exchange of labor for money. I'm very happy for them, and hope we can all make such great exchanges. This fellow sounds like a real go-getter, and we need more such inspirational people.
That doesn't mean that the employee is to blame, this is purely a problem with BART management -- instead of paying one person 4X normal salary for a job (even if he's working 100 hours/week, that's still "only" 2.5 times a single worker), they should have hired 4 workers for that job, or if it's transient work that doesn't need a full time worker, then hire a contractor(s).
http://www.indeed.com/salary?q1=janitor&l1=san+francisco&tm=...
If one can overtime their way to 2-4x avg salary, so can anybody. The question is do you want to. If the answer is no, blaming the guy working hard to make 4x the base salary is unfair. Plus there is no social contract that if one worker makes less, so should others.
You can't force people to be lazy, you can't force them to be hardworking. A lot of times the world is fair, and you get what you deserve.
And make no mistake: almost everybody commenting in this thread is a member of the lower classes, even those of us pulling down six-figure salaries in the high $100k-$200k range. That some of us are relatively higher than others is immaterial to the immense wealth commanded by those in the class above ours. We have far more in common with the "lowly" janitor than these elites have with us.