IIRC, You can only use Sprint flashed phones on MetroPCS network, other than of course MetroPCS Phones.
According to Wiki,
CDMA is used by Verizon, Sprint, US Cellular, Tracphone, Virgin Mobile, Quest, Cellular south, and several other smaller companies, so I believe you can use those as well, if you can get someone to flash the software.
Also, just be aware I have heard that if you flash the phone, they don't always function 100 percent, such as I have heard of them not working on the Internet.
Only a
CDMA Phone can be used on Metro PCS, so only Sprint, Verizon, and the like.