It doesn't look like the information about posts being migrated (PostHistory.PostHistoryType=17) is stored in the data dump. The best data we have is is in the migrations section of the 10k tools

In the last 90 days

    SU        323
    SO         77 
    U&L        44
    DBA        33
    Apple      32
    Webmasters 27
    AskUbuntu  20
    Security   17
    mSF         1
    
    Others     12 to 6 different sites