If Facebook locates offices in areas with a high cost of living they need to factor that high cost of living across all their employees - including cleaners, security guards, admin clerks, and other low pay workers. Facebook can't just use national average wage for the type of job for those jobs, Facebook needs to pay for the increased cost of living for all those people.
That is built in to how the world works: They cannot pay middle-of-nowhere-china salaries of $5/day to cleaners and security guards, even though those middle-of-nowhere-china residents are willing to take it because they cannot commute there to do the work (for transportation, legal and other reasons).
If facebook is paying wages that are too low, they will not find employees.
While I definitely agree with the sentiment that jobs should provide a living wage, and I suspect that driving a bus for facebook might not provide that - I think singling out companies that are doing well financially (like Facebook and Google) and asking them to increase pay is hypocritical. If the pay needs to be higher, that should be codified by law.
I would oppose a protest asking Bill Gates (whom I do not particularly like, btw) to pay more at the grocery store for same services as anyone else just because he can, regardless of whether the person at the register is making a living wage or not. And facebook paying drivers more is similar.
But if Bill Gates wnted to empty the grocery store of other customers before he went shopping you would charge him more.
Facebook don't want Muni buses and Muni uus drivers, they want exclusive buses and that creates extra costs which they need to pay for. Here the extra costs come from exclusivity and split shifts.
I don't understand the relevance. They are not monopolizing muni busses and muni drivers. On the contrary, they are creating more venues (Bill Gates would pay someone to run his own private grocery in this awfully-stretched-and-no-longer-fitting analogy).
They are happy to pay for the extra costs - but not more than they need to. Now, the question is "how much do they need to pay for that" - and historically, this answer is reached by matching supply and demand subject to regulations.
The bus drivers might want to increase the price (by reducing supply - that is, in fact, a union's leverage). Facebook might counter by hiring a different bus company.
If the wage is not livable, they will not find drivers because those drivers need to eat. If the wage is livable and there are willing employees - why should they pay more? "Because they can" is an answer I personally find unacceptable.
