Late last month, reports surfaced indicating that the iPhone 5 would be launching with T-Mobile, at the same time it launches with AT&T and Verizon (whenever that might be).

The rumor was sourced to a T-Mobile contact that claimed to have been briefed about the upcoming device. MacTrast quoted the source as saying –

The informant, who requested to remain anonymous, went on to claim that the iPhone 5 would also operate at 3G speeds on T-Mobile US network. Current unlocked iPhone 4 units can only operate at 2G “edge” speeds on T-Mobile’s network, and lack certain network-dependent features, such as Visual Voicemail.

Further elaborating on the matter, the informant suggested that T-Mobile USA expects the iPhone 5 to launch sometime in early to mid October, which corresponds nicely with current speculation.

This rumor popped up just days after rumors emerged surrounding Sprint’s launch of the iPhone 5. Since that time, numerous reports have come out backing the prediction that the device will indeed arrive on Sprint sometime in October.

Now we get our first corresponding rumor surrounding the previous T-Mobile/iPhone buzz. T-Mobile blog TmoNews has obtained what they claim to be an internal email sent to T-Mobile employees. The email asks employees to “save the date” for an all hands meeting on Saturday, September 24th.

Their analysis of this cryptic document is pretty amusing –

Could this be a pre-iPhone launch meeting? Could this be related to the AT&T takeover or could this be related to T-Mobile discovering water on Mars? In any case, mark your calendars down for September 24th because something is going down.

While this email doesn’t specifically mention an iPhone 5, it does let us know that something big is going down near the end of September in the world of T-Mobile. Previous speculations have put the iPhone 5 pre-sales starting in late September.

But then again, there is a lot of other stuff going on at T-Mobile right now involving a particularly noteworthy acquisition that is running into some serious roadblocks.