MagicalTux has already stated that mtgox doesn't trade at all because it would be unfair, or at least look that way.  That may or may not be true, but I don't consider the whining of lousy traders or the insane speculation of conspiracy theory nuts to be evidence in either direction.

If someone does have actual evidence, I would love to see it, as would everyone else, I'm sure.  That none has appeared seems to say a lot, even if it is neither conclusive nor final.