I have worked in many overseas development projects run by Chinese companies. It's not that the Chinese companies only want to hire their own workers, but the fact that the local workforce do not have the skill/equipment/capital to handle large scale development projects.

Some countries require by law that the Chinese developers have a minimum number of local workers. This mitigates the problem somewhat and hopefully over time the locals will develop the skills to run their own projects.

In the long run, infrastructure investment benefits local communities and opens up more opportunities for the local workforce. It's almost always better to have the infrastructure built than not, earlier than later, and foreign money is a good source of capital for it.