Owners of T-Mobile’s Nexus S are waking up to a pleasant surprise this morning:  T-Mobile has finally started to allow use of Google Talk’s video chat service over their 3G and HSPA+ networks.

When the service was originally launched for Android 2.3.4+ devices (read:  Nexus S) back in May, owners of the Nexus S rejoiced at the thought of what their devices would soon be able to do. Previously only available on Honeycomb devices, Nexus S owners would soon be using Google’s Talk service to have video chat sessions with just about anybody who was connected to the internet and had a Google account. And they were going to be able to do it without needing to be tied down to a Wi-Fi network.

At least, that was how the story went in theory.

A little over a week ago, our own Russell Holly lamented that T-Mobile was still preventing users from using this service over their cellular networks, requiring users be connected to Wi-Fi to utilize video chat. Since this functionality was still available on Sprint’s Nexus S 4G, all signs pointed to T-Mobile being the culprit (though unsurprisingly Magenta was silent as to why it was taking them so long to enable this functionality).

According to a post on Android Police (Thanks, David), it turns out T-Mobile blocks the special P2P mode that Google Talk’s video chat service uses to connect users together. They needed to figure out a way to enable that mode for Google Talk while still blocking other kinds of P2P connections that use the same mode.

Though it has taken Magenta over a month to get the P2P issue fully resolved, T-Mobile Nexus S owners can rejoice that video chat is finally here. This also hopefully paves the way for other T-Mobile devices once they receive the update to 2.3.4 (or beyond).

Are you one of the lucky T-Mobile Nexus S owners waking up to video chat this morning? Let us know how it’s working for you in the comments.