According to the PDF posted in this response (Can we get a complete list of information that will be stored in dop files? - #7 by sgospodarenko) to an old thread of mine, the ShouldProcess attribute of the DOP file should indicate the pick/reject flags. All files that I have picked had ShouldProcess set to 0, the rejected one have ShouldProcess set to 1 and I assume (I didn’t verify this!) that ShouldProcess set to 2 means they are untagged (that’s the wording used in the filter section which also contains the picked and rejected options).