Scene was the original season 2 opener. The idea was to introduce the new threat and elude to the gov. This was shitcanned and they decided to not even open the can of worms. It was meant as an open door for the gov, and would add to the Merle story ( remember the Merle says the gov saved him in atl ).
And, because I'm just that kinda guy, Darabont originally intended a totally different premier than S2e1.
It would have been the last days of Atlanta, with the Army defending the city. Basically, Black Hawk Down for 44 minutes with zombies. It would have followed an unnamed soldier fighting thru the city. In the end, he's bitten and surrounded, so he opens the hatch to a tank and climbs in to die. Well kinda die, cause Rick meets him when he climbs into the same tank. Episode 2 would have them leaving the CDC.
I've "heard" Darabont got far into the writing phase of this, but Kirkman and AMC decided it was not the direction to go. AMC felt it would be expensive, and while Kirkman seems like a cool guy on paper, in hush hush is he's kinda a controlling prick about his product, to the point two showrunners have left.