Performance monitoring of colocation vendors

Hello,

If a company uses a co-location facility for housing its IT
infrastructure:

1. What are things that are appropriate and necessary to review/audit
the service provider for on a regular basis (e.g., annually)? Does
anyone know of a good checklist or an audit program for such review?
Is it appropriate to ask the vendor to provide for review internal
policies and procedures for equipment maintenance, incident handling,
physical access, etc?
How should I handle situations when the colocation provider with whom
our company has a colocation contract has outsourced the facilities
management to another company and says that the maintenance P&Ps are
part of the contract b/w the outsourced vendor and them and are
confidential?
What is an appropriate way to leverage SAS70 reviews on the vendor?

2.  What are appropriate metrics to use to "monitor" the performance of
the service provider (if they are providing facility and internet
connectivity)?
Up-time, power outages, environmental parameters, incidents, etc.

Thanks!