Interesting question. My initial reaction is that yes, it is a standard exam, but I suppose if you look at it in detail, the IELTS speaking paper is a bit less standard than those in the Cambridge ESOL exams, as the examiner is allowed to go off-script a bit with follow-up questions.
What do you think?
I agree with you about the speaking paper. But I think we cannot call it a standard exam. According to the results, people who pass IELTS exams are not very knowledgeable. They just learn some tricks to answer questions correctly. But in Cambridge ESOL Examinations the story is completely different. Nobody can pass the exams without having the knowledge.