I just came across this post. It was not in the Xtraction section (which I try to monitor), so I did not see it until now. I am going to move it to the Xtraction area after posting my reply.
Did you ever get this problem resolved?
The logic of your Advanced Filter does look correct; however, are you sure you want to restrict the customers to only seeing this month's metrics? If you don't want to restrict the age of the data in the data policy, then it would simply look like this:
Company equals A
Company equals B
Customer Site equals 1
If you were not able to identify your problem (like you were seeing no results because no data was submitted during the current month), then you may have come across a bug.