greg - I'm no expert but have redeemed similarly before for tickets when in a bind (100 miles per $).

Note your choice account separately notes MP-visa-earned and non-MP-via-earned miles, and you can only "redeem" from the visa-earned miles. Regardless though yes these are miles from your MP account.

I guess I am confused though - where did you think the 40,000 miles were going to be deducted from?? Your delta account?