As bigsnake said, KDDI still has their network in Japan, there are a few European operators that still have 450mhz CDMA networks for critical use and rural/low-population areas, and, as I mentioned, the largest CDMA operator in the world, China Telecom.
They are doing some work out here in Pinckney... They added 800MHz panels to the main tower by my house and they should be activating it soon. I'm planning on switching my main lines back to Sprint once it happens.
It's treated much like Sprint's extended roaming partners like USCC, though it may be subject to a 5Mbps speed cap (I don't remember for sure, but I don't recall going over 5Mbps when I was roaming on Viaero last summer when I had T-Mobile.)