Is it enough of a problem, network operators would be interested in
publishing some Practical Common Practices (I hesitate to call it a BCP)
collocation facilities could follow for some common access control
scenarios? Tenent access, pre-screened carrier, unscreened vendor, etc.
http://www.ncs.gov/nstac/reports/2005/Final%20TATF%20Report%2004-25-05.pdf
I wouldn't be surprised if most co-lo's don't actually have good reasons
why they do some things, and if presented with a reasonable industry
agreed practice, would adopt it.