The M&M integrated carriers are: Adria Airways, Air Dolomiti, Austrian Airlines, Croatia Airlines, LOT Polish Airlines, Lufthansa and SWISS.

The double miles register when you buy anything from the above airlines. So if you buy a ticket on United but get LH to issue it and charge the ticket to the M&M MC, you will get double miles. The same applies for duty free purchases onboard LH and buying something at the Worldshop in MUC & FRA. I got double miles for all of the above