Question:
Which area of maintenance do you subcontract, if any?

http://www.redorbit.com/news/technology/437435/248_mill...?source=r_technology

What lead to the decision?

Choices:
All maintenance functions are subcontracted
Planning function subcontracted
Big / complex jobs subcontracted
Partial maintenance is subcontracted
None

 

I will give an academic answer: it all depends!
When I worked in power generation, the only work outsouced was specialist stuff like leak sealing or lagging.

Some of the companies run that way still, but do bring in up to hundreds of workers under contracts for major outages.

Some use partnering, where a contractor IS the maintenance department.

Some share the benefits as well as any losses in an open book arrangement.