Presumably the drivers think the contract was already breached by the company, which therefore rendered the drivers' side of the bargain "null and void" or something similar.
In this particular case, I think that is unlikely because the bus drivers are in the public view.
However, it raises an important issue. Contracts guaranteeing working conditions for indentured servitude are often unenforceable. I think unenforceable contracts should be outlawed. I also think States should set minimal contractual conditions to prevent incomplete contracts.
For example, consider the 3 year term imported bond servants in Singapore. Singapore is quite libertarian with respect to its treatment of foreign nationals. Paternalism only applies to citizens. The standard contract requires 3*24/7/365 service except for leave provided at the master's pleasure. To reiterate, the servant cannot legally leave the master's house without permission.
How does one seek contract enforcement from the confines of a cell? For example, lack of recourse in cases of rape is a frequent issue. How does one enforce protection from rape when the rape victim cannot lawfully communicate with the outside world? Moreover, contracts are always incomplete. If the contract does not prohibit an abuse, is that abuse then permissible? It is a simple matter to trick illiterates from Myanmar into signing incomplete contracts. We do it every day.
Everyone in Singapore lives in a skyscraper. Every year in Singapore, 20 domestic servants "fall" from skyscrapers to their deaths. That is an annual "fall from height" rate of about 1 in 15,000 per servant-year, or 1 in 5,000 per servant-contract. Two principal reasons:
1) Master requires domestic servant to clean exterior windows without safety equipment. Most maids survive and maids are cheaply replaced. Safety equipment is expensive.
2) Domestic servants abscond from their cells via the windows. Death can be preferable to serving a contract term.
a) Is it really okay to force someone to choose between carrying out a contract and suicide?
b) If not, then how can a contract that cuts someone off from the outside world for 3 years be allowed? Such contracts will always result semi-frequent cases of (a).
Now, servants benefit from the contracts on average. They get higher wages and serious abuses occur in only a minority of cases. Does that make these contracts moral? I have to deviate from the free market logic here and say no. What do you think?
[Here is something very funny BTW. Singapore has a quasi-fixed exchange rate, so we can't do any Keynesian shenanigans. How does the state cool down inflation? Import foreign nationals to lower labor demand for citizens. How does the state stimulate a sluggish economy? Forcibly deport foreign nationals to raise labor demand. Unlike weak Keynesian states, we don't fuck with the money supply, no need lah. The state simply trades in poor people. It is a 'sound money' alternative to Keynesian stimulus. LOL as the Sing Dollar appreciates.]