Sorry Null, don't have links or details, but I'm sure I've read some abstracts over the years where there was simultaneous muscle growth and fat loss. They may have said "lean mass gained" but it was clear from context that they meant muscle growth. These effects didn't necessarily cancel each other out (i.e. fat loss didn't equal muscle gained). They always seem to involve overweight subjects that were out of shape (perhaps totally untrained) before the study began.
I didn't bother to try to read the full papers because they weren't what I was looking for. Yes, there are potential confounding factors and measurement errors. No, I don't know if/how they tried to control for those factors.