https://support.apple.com/kb/sp655?locale=en_US notes 3 models of which for GSM systems I encounter the first and last. It's not always possible for me to decode which LTE channel the carrier will employ and Tmobile can not answer since you only know "iPhone 5" which there are 3.

Example:
"GSM model A1428*: UMTS/HSPA+/DC-HSDPA (850, 900, 1700/2100, 1900, 2100 MHz); GSM/EDGE (850, 900, 1800, 1900 MHz); LTE (Bands 4 and 17)
CDMA model A1429*: CDMA EV-DO Rev. A and Rev. B (800, 1900, 2100 MHz); UMTS/HSPA+/DC-HSDPA (850, 900, 1900, 2100 MHz); GSM/EDGE (850, 900, 1800, 1900 MHz); LTE (Bands 1, 3, 5, 13, 25)
GSM model A1429*: UMTS/HSPA+/DC-HSDPA (850, 900, 1900, 2100 MHz); GSM/EDGE (850, 900, 1800, 1900 MHz); LTE (Bands 1, 3, 5)"

As to speed, my sure bet is it will be faster than 2G if it works. My bet is it will work.