XO - a Tier 1 or not?

Trying to sort through the marketecture and salesman speak and get a definitive answer. I figure the NANOGers would be able to give me some input. Is XO Communications a Tier 1 ISP? I'd say no based on all research and googling that I've done but they seem to meet some of the criteria (some != all and therefore not Tier 1). Any help here? Thanks as always. Chuck