This debate has raged on for years. What is a Tier 1 provider? Who is a Tier 1 provider? Well, Grant Kirkwood, CTO of Mzima Networks, has decided to write a novel about it at techistan.
Mzima resells transport from the other carriers and adds its own special sauce of management. It mostly sells Ethernet. It was acquired by PacketExchange this month. (I rep for Mzima).