NBC decided to pass on Mockingbird Lane after seeing the pilot, but having spent so much money on the pilot, decided to air it anyway. The premise being that by airing it they at least recover some of the millions they spent on the pilot. HitFix's Alan Sepinwall refers to the airings of passed-on pilots as "Busted Pilot Theater" which used to happen more frequently.
Regardless of anyone trying to spin it as a test run, the reasonable conclusion is it was "Busted Pilot Theater" and nothing more. But the preliminary 1.5 adults 18-49 rating for Mockingbird Lane outperformed originals of Blue Bloods and CSI: NY as well as the premiere of Kitchen Nightmares (which it aired directly against) and served as a decent lead-in to Grimm (which was up 27% from last week.).
For me, the reasonable conclusion still is "Busted Pilot Theater" and that its performance last night doesn't mean NBC will be scrambling to figure out how to start the series back up. But if nothing else this will add a log on the fire of "look, people want something different see 'The Walking Dead,' 'American Horror Story' and 'Grimm!'"