In some instances, even with Roland gear, it appears that the DP-10 only sends (or the unit only sees) three values, 0, 64 (half), and 127 (full). Not the pedal's fault, but interoperability with different instruments does not appear to be consistent:
http://forum.pianoworld.com/ubbthreads.php/topics/2901103/1/roland-dp10-pedal-is-it-actually-continuous.html
Roland DP10 is a 'continuous' pedal in theory, able to send range of 0-127 velocity levels for sustain. And it apparently does, when used with FP30 for example. When connected to FP10, and then FP10 via USB MIDI to laptop, only single values 0,64,127 are being transmitted.
@pawelsz is likely correct in that the polarity may need to be reversed to be used with the Montage.
-dj