[jabretti]

You could contract different lines out to different companies. I think Tokyo does this.

At the very least, though, you could contract out the running of the whole system to a company for five years a time and let different companies compete for the contract every five years.

This isn't a panacea, but it can sometimes help if the main problem is corruption-induced inefficiency as it seems to be for most major cities in the US.

[rtkwe]

You'd need some kind of long term planning guidance behind that though because anything beyond the most surface level changes or additions to the system is going to take longer than 5 years and what contracting company is going sink millions of dollars into a system they're only guaranteed to be running for the next couple years?

[Anechoic]

The MBTA in Boston does this with its commuter rail lines. Currently the contract is held by Keolis, before that, a consortium of companies led by Veolia Transportation. You can Google "MBTA commuter rail performance" to see how well that's worked out.