Gives details of past flights and their New First usage.
The BA207 is 50% of the time with NF and the BA209 64%.
It does appear when NF is not used then it is some of the very early Mid-J aircraft, G-BNLR / G-BNLY etc.
Looking at the history http://ftdashboard.net/dest/mia.htm you can see that more and more flights are operating with the NF though than earlier in the year, as aircraft are still being retro fitted.
Sorry cant give you a definite, but its at least better than 50/50 chance!