I don't know if the police would involve the FBI in a meth lab op or not. Close to where I live earlier this year, the police called the FBI in to assist when ricin was found in a house. But in that case, the police knew immediately what it was.
I would think the Tuscon police would be able to tell immediately whether a scene is a meth lab. There are certain things you need to make meth, and the police know what those things are; and if they're found in a house, the police can be pretty sure what was going on. But the news articles seem to suggest the number and nature of the chemicals found in this house have left the cops completely confused. That makes me more suspicious that it isn't something so (relatively) mundane as a meth lab.