http://support.t-mobile.com/thread/44406
This post sums it up pretty well.
"In absence of reliable INFORMATION, you will really need GOOD LUCK bringing an iPhone or other unlocked device having 1900 MHz band but not supporting T-Mobile's native 1700/2100 MHz AWS-coverage."
The network frequencies for the mentioned 3 phones are as follows.
HTC Butterfly S
HSPA/WCDMA:
- 850/900/1900/2100 MHz
GSM/GPRS/EDGE:
- 850/900/1800/1900 MHz
Xperia ZL
UMTS HSPA+ (Bands 1、5、8 OR bands 1、2、4、5、8) *
‧GSM GPRS/EDGE 850、900、1800、1900 MHz
‧LTE (Bands 1、3、5、7、8、20 OR bands 1、2、4、5、17)*
Xperia ZR
‧UMTS HSPA+ 900 (Band VIII)、
2100 (Band I) Mhz (並非所有市場皆提供)
‧UMTS HSPA+ 850 (Band V)、1700 (Band IV)、
1900 (Band II)、2100 (Band I) (並非所有市場皆提供)
‧GSM GPRS/EDGE 850, 900, 1800, 1900 MHz
All I want to know is, refarm ambiguities aside (cough cough), if I can get speeds faster than EDGE on any of these phones, like HSPA(+) or even the "new" LTE, which is on 1700&2100, from my understanding.