... So - that is the larger picture, but was not my question to NANOG.
We wish to be able to provide this peering, but we find that UUnets cross-connect policy interferes with our aims - as it requires potential peers in the data center to separately purchase connectivity to us (in the same building) instead of hopping onto our link by cross-connecting to another cabinet in the data center, which (of course) they waive for connections to the CINX cabinet.
My question was if this was common practice.
yes, it's common for a hosting facility (which uunet cape town is.) it would not be common in a carrier/fiber hotel. if there is one of those in town you'd be well served to talk to the landlord about supporting a peering exchange there, since it will drive other sales, and the openness of it will ultimately pull business away from the necessarily-more-closed peering exchange over in the hosting center.