I don't think it's equivalent.

In fact, I've come to really dislike the Cogat test. My HG+ ds has taken it twice and both times not scored above 92%. However, he's taken the WPPSI, SB5 and the WISC-IV twice. On each of these he scored 99%+. I wish I could find more research on the inaccuracies of this test for HG students. It cares quite a bit of weight in many school systems when working on GT placement.
Anyone know of a source?