[VOIPSEC] An issue of trust?

[Ron_Cramer at cargill.com]

The issue of trust for your Telecom service provider, 
either traditional or VoIP based seems to be a fundamental
component for secure communications.

Can anyone identify an industry standard that an 
Enterprise can use to establish trust with a Telecom
vendor?  Something with well established decision
criteria, not just a high level guide to performing a
risk assessment.

Thanks in advance,

Ron