What you could do perhaps (but I don't know the legality of that) is reverse engineer the way the audio is changed by Dolby Headphone. Some things I could think of is a stereo audio file with white noise in the left channel and silence in the right one, then look at the frequencies in the resulting right channel after the filter to find out how the various frequencies are amplified.
To find the delays, maybe you can do the same but with a frequency sweep in the left channel and compare the resulting right channel to the original left one.
Then there also is the (possible) phase change...
Not sure what is the best way to test all of this, perhaps someone else here has an idea for a better/faster method.