Had some MFMs when I was younger with straight guys, and I thought myself straight at the time. As Tekken says, MM body contact is unavoidable and I found it exciting, but nothing happened. These days things DO happen!
In a MFM all of the attention is on the woman but hands and dicks do meet. Not a big deal, both of the M's are into the woman. I have had my hands and dick hit the other dick and his hands and dick hit mine and we both went on taking care of business.
If you are in a MFM situation and you are worried about crossing swords obviously you should not be in a MFM situation. If it's 2 heterosexual men (Like the others have said) the last thing on your mind should be the other guys dick. The focus would be the woman and if you just so happen to tangle tea bags then who cares. It's not as if you are in the other guys ass.
I have had many MFM experiences, all that I have paid for through net ads. Much of the experience was role play in scenes that were similar to a cuckold fantasy of mine. As to the answer to the question, yes there was some contact but I didn't find it a big deal since not much happened.