Each wireless carrier will independently decide when it can/will release their first BlackBerry device. We've seen instances where for no apparent reason, some devices are delayed with certain companies over others (AT&T and the Bold 9900, for example). With BlackBerry 10, this will probably be the same.
The launch event is on the 30th of January, as we've told you many times already and it appears the first two carrier release dates are starting to come out.
According to TMoNews.com's leaked T-Mobile roadmap, the L-Series (in T-Mobile's case the Lisbon), won't see the light of day publicly until March 27th. That's a long ass time after the launch and we're obviously hoping it doesn't pan out to be right.
Roadmaps like this aren't always 100% accurate though because we don't know exactly how old it is. Many times, carriers have changed dates because of different circumstances that eventually make these roadmap guidelines obsolete.
Also leaked today, is an indication that Canadian carrier Bell, will be releasing their L-Series/Z10 device on February 28th, almost a month before T-Mobile's speculated release.
Let us know what you think about these release dates in the comments!