As an ex-IELTS Examiner I can tell you that all IELTS examiners are expected to meet the same standards wherever they examine. However, there are some things that most people probably <u>don't</u> know.
1st of all, although in the speaking test training ielts examiners are trained on a variety of accents, we usually struggle with different accents. This is just the way people are. We get used to a particular accent. So, usually an IELTS examiner will be a little bit more lenient in the pronunciation section. This difference will be minor. For example, instead of a "5" in pronunciation, you may get a "6".
This small difference can be just enough to bump your speaking over from 5.5 to 6, or 6 yo 6.5. So, if you are a borderline student, I recommend taking the exam in the country of your birth if possible. However, it should not make any difference for 7 or higher because you should be generally natural at this point.
Hope this helps!