What a coincidence. I was skimming the P-61 entry on Wikipedia just yesterday and read the following...
"A P-61 was supposed to be featured in the historically accurate 2005 John Dahl film, The Great Raid, where the P-61 served as a distraction as United States Army Rangers crawled across a field in daylight during a key moment of the Raid at Cabanatuan. However in the actual movie, it was played by a Lockheed Hudson, "VH-KOY."
A quick Google search revealed a photo link to the plane in question...
http://www.planepictures.net/netshow.php?id=471879
I would have to look at the film again to ID the fighters -- but, for such a brief scene I suspect that they may have used Computer Generated models.