According to http://www.wowwiki.com/Goblin_Engineering it's 30th level
but
According to http://wow.allakhazam.com/db/quest.html?wquest=3526 it's 47th level
I'm 31 with a 202 engineering, so I'm suspecting the 47th level might be the one as I'm currently sitting in front of the engineering trainers in Org and they've got nothing to say to me.