this is all from memory so dont take anything i say for 100% truth but i think im pretty accurate in what im about to say...
i believe that the dewalt saw will work with a festool rail (festool saw howerver will not fit the dewalt track), your saw should have two groves in the base plate.. this would obviously be the easiest way to use the mft, especially if you bought it as a complete set which includes the rail.. ready to cut right out of the box!
fyi, expect some adjustment of the cams in the saws base plate when switching between the festool and dewalt rail
if for some reason you wanted to try to sell the festool guiderail and use your dewalt rail i think you will still be in the clear, although it might require slight modification
i dont think a festool clamp will work with the dewalt rail, (the small dimension of the slot opening at the very bottom of the rail is too tight i think, not the widest internial slot width) which means the front track alignment tab on the mft wont fit into the slot in the bottom of the dewalt rail, with some very careful filing of the tab this could be remedied, make sure you dont remove to much tab material and introduce slop
the rear hinge portion of the mft rail mount uses a metal bar and two bolts to clamp the rail in place... something tells me this will work fine ( im guessing that the diameter of the bolts is small enough to fit through that tightest dimension of the dewalt rail slot.
hope this helps, Good luck!
John