I just ran into our missing friends, the Engineering cogs on the trainer in Stormwind today. We had a new build on the Beta realms yesterday and apparently they put more goodies in for professions. These new cogs are learned at 550. Here are some pics I took:
The cogwheels can go into items as low as ilevel 417, but I don't know that there actually are any items that low with cogwheel sockets. At this time the only engineered items you can socket with cogs are the new helm and the dragonling trinket.