Got a chuckle from T-Mobile Rep recently.
He said that T-Mobile is able to "do" roaming because their
phones also "tuned" to other's analog and
GSM, such as ATT
and Gingular.
Whereas, "Sprint can't do roaming" because Sprint has their
own system that is exclusively
CDMA.
I didn't tell him that yes Sprint itself is exclusively
CDMA, but dual-band phones "tuned" for Sprint PCS service
are also "tuned" for analog roaming, and the SPCS
dual-band/tri-mode phones can also do roaming both analog
and digital.