I don't think those two actions are linked together.
As I understand, for every 32 shares you already own of EMXC, you will receive 1 share of MPIX (they will show up in your brokerage account automatically).
The share buy back is different and should happen without even you being notified of it. The company has not divulged how many shares they'll buy back (except saying by 10s of millions at a time). Now shares buy back is in no way changing the shares structure and they are still available to flood the market if they chose to do so.
Hope this helps you? I am not a financial person but this happened to me in with previous securities.
Disclaimer:
Everything you read from me is under the usual IMHO.
Do your own DD as I am not responsible for any decision you may take reading my guts feelings...