While it isn’t quite the AT&T-T-Mobile blockbuster, the move has broad implications on the mobile communications industry.

Google (GOOG) and Sprint (S) just announced that the two companies would soon be integrating their voice services.  The deal is two fold:

First, Sprint customers will be able to use their existing Sprint mobile number as their Google Voice number and have it ring multiple other phones simultaneously. So now, calls to your Sprint mobile number can easily be answered from your office or your home phone, or even your computer through Gmail. Calls from Gmail and text messages sent from google.com/voice will also display your Sprint number. This basically gives Sprint customers all the benefits of Google Voice without the need to change or port their number.

Alternatively, Google Voice users can choose to replace their Sprint number with their Google Voice number when placing calls or sending text messages from their Sprint handset. This feature works on all Sprint phones and gives Sprint users all the benefits of Google Voice without the need for an app.

In both cases, Google Voice replaces Sprint voicemail, giving Sprint customers transcribed voicemail messages available online and sent via email and/or text message. International calls made from Google Voice users’ Sprint phones will be connected by Google Voice at our very low rates, and Sprint customers will also have access to the rest of Google Voice’s features, like creating  personalized voicemail greetings based on who’s calling, call recording, blocking unwanted callers, and more.

Roll the video:

[youtube=http://www.youtube.com/watch?v=Rp8Wvknh_QQ&w=600&h=375]

So, in effect, Sprint is happily handing a large chunk of its backend voice and texting services over to Google.

The move is great for both companies.  Here’s why:

Sprint doesn’t bill or earn much money on voicemail or call forwarding features.  Offloading those to Google will provide operational cost savings and, at the same time, offer its customers a best of breed differentiator in phone services.  Google will get to connect long distance calls, which it can do for much less than the major mobile carriers because of its all-IP global infrastructure.

The service is optional but it offers so much above and beyond normal voice services that it seems hard to imagine that most people won’t jump in.  It is available to all Sprint users, even those with feature phones, free of charge.

The service, at least initially, is only available to Sprint’s post-paid customers and isn’t available to business customers or customers on Sprint’s MVNOs like Virgin or Boost.

The service will roll out gradually over the next few weeks.  It just might be enough momentum to get people in the telecoms space to talk about something besides AT&T (T) and T-Mobile.

Sprint also announced it would be carrying a 4G version of the Google Nexus S Android phone, which has Google Voice additions built-in.