For what it's worth, I was recently rejected from joining BBJJ because I have a blue belt from another school. I think the defining factor in their decision was the fact that I expressed interested in returning to my first school over the summer, when I have a break from studying in Brooklyn.
They are not interested in those who are interested in competing, and they generally do not think those who have previously trained elsewhere are capable of making the transition to their system. (This is almost their exact words).