Windows Phone NoDo update to arrive April 19th for AT&T phones (Updated)

A leaked internal communication confirms the Windows Phone NoDo update will land on AT&T handsets starting April 19th. The carrier has completed testing of the first Windows Phone update and will roll it out to the LG Quantum and Samsung Focus on April 19. For some unknown reason, HTC Surround owners will have to wait until mid-May for the release to become available for their handset.
According to the document, the update will require two steps. Users must first install the pre-update for NoDo and then the NoDo update using the Zune software. The carrier confirms the update includes copy and paste as well as some unidentified features unique to these AT&T branded handsets. Finally, some good news for Windows Phone owners on AT&T who have waited patiently to finally get the NoDo update and capture the full copy and paste experience.
For those who are interested, the full text of the internal AT&T memo is on the second page for your reading pleasure. You can also check out the Windows Phone update page for more information.
Update: Microsoft confirmed in a blog post that the NoDo update for the Samsung Focus and the LG Quantum passed carrier testing. The Redmond company also clarified the reason behind the delay for the HTC Surround with the following statement:

The updates we deliver contain a complex stew of software code. The content often includes not only our fixes and improvements but also software supplied by companies that make the phone itself and the chips inside it. One of these third-party software “packages” earmarked for the HTC Surround needs additional testing by both Microsoft and AT&T. I apologize for the delay. As soon as I have more news, I’ll let you know.