I am assuming that you do not have matching timecode.
Here you are running into the limitations of Avids multicam implementation.
Your options are, I believe:
a. Do mix downs (or QT ref exports and reimport)
b. Amend aux timecode for each clip so that they correlate to shoot time of day – then you can multi-group by timecode
c. At each edit point in your assembly sequence – Match frame to every clip in the stack and then group those clips by in point. Name the group appropriately (eg the mark in point for cam1 ) and edit onto new video layer up to the next edit point. (Good idea to also add audio)
Subsequence that top video track and corresponding audios and you have a multicam grouped assembly to edit from.
C is best/easiest option but I wish Avid would automate it. Doing it more and more as I get spanned clips on multiple cameras. And encourage shooters to use time of day – now that tape is dead we don’t care about preroll.