T-Mobile's response has been added to this story. NEW YORK ( TheStreet) - At last week's introduction of the new BlackBerry ( BBRY) 10 smartphones we were told that all four major US carriers would soon be selling the new Z10 touchscreen device. Within a few hours three of the four carriers declared their intentions. T-Mobile kept mum. And now we're beginning to understand why. According to rumors, T-Mobile has big plans for its Z10 introduction. The Tmo News Web site has spotted an internal T-Mobile Web page that shows a March 27 launch date for both the Z10 phone and T-Mobile's upcoming LTE/4G network. Actually, we're not all that surprised by this possibility. At BlackBerry's big event last week, we placed a T-Mobile SIM card in a new phone and were amazed to be greeted with a full-screen T-Mobile logo. We had been told that the test unit was made to be used only on AT&T's ( T) network. We've found that the Z10 works very well on T-Mobile's slower 4G frequencies right now. Hopefully those new T-Mobile LTE frequencies will be recognized by new BlackBerrys as soon as they're turned on. It looks like there will also be a new Samsung Galaxy SIII LTE and Galaxy Exhibit handsets introduced at the same time, as well as a 4G/LTE Sonic 2.0 "hotspot". T-Mobile's current Galaxy Note II tablet/phone is reportedly only a software update away from being able to operate on the new LTE network. What's not yet listed - at least not until Apple ( AAPL) formally announces it themselves - is the often rumored T-Mobile iPhone 5, which the carrier can't wait to start selling. T-Mobile declined to comment on this story when contacted by TheStreet. Back to BlackBerry; there's also news that the handset maker has readied some early production Q10 handsets (its new devices with a touchscreen and real QWERTY hardware keyboards), as well as a very "hot" cherry red Z10 - both for software developers only (at the moment, anyway). --Written by Gary Krakow in New York. >To submit a news tip, send an email to: firstname.lastname@example.org.