Based on a TAC case I have open at the moment the answer appears to be no. Apparently, once the MTP is allocated a final codec selection is chosen between the MTP and the calling endpoint. The final called party must support that codec or a transcoder will be invoked.
I'll try to remember to update this thread in a few days based on the final answer from the BU. If not bump it to remind me or have TAC query 615746593.