S.,
I do not agree with the posters that he should have to clean up his mess, regardless of why he is doing it...it is dangerous for a child that age to be digging around in feces...they are not able to "clean" it or themselves up properly or sanitarily and it is frankly humiliating. As a side note, it is not unusual for the child not to admit that he messed his pants. No one wants that embarrassment in front of people, we don't even admit passing gas most of the time.
I am sorry for your friend, but she "bought the pony" so to speak. What she needs to do is treat the situation with love and patience. First of all, she should treat it as a medical condition until she knows otherwise. Once she has him cleared, she should not assume it is just laziness...that doensn't make sense, especially because the embarassment would far outweigh the benefits. That said, tell her to have him wear "good-nights" to school and at home. Have her discuss with him that it isn't his fault that he wets the bed sometimes at night, that even big-boys sometimes do (my husband was 8 when he finally stopped), but that it is not ok to do it during the day. Have her reserve the "Good Nights" for night time, but see if she can get a large size diaper and tell him that until he can go like a big boy, she will need to have him wear those and get changed like a baby. This may actually be what he wants if there is a bonding issue that he is trying to overcome. I know this sounds kind of weird, but she could do that for a week and then "potty train him" all over again with rewards for going in the potty (or she could just skip to the reward motivation chart...no poop no pee in the pants and he gets a treat or extra TV or something).
If he has enuresis (nighttime bedwetting) a lot of times that is due to a small bladder that can't keep up with urine production, but I have heard that milk sensitivities can cause the wetting, so have her cut out milk after noon and see if that helps at all.
I tend to believe that the new-mother thing is the real issue. I have limited faith in "counseling" and feel that open communication between people works best. Your friend needs to sit down and think about how she fits into his life and how she wants to explain her role to him. Does he have a Mother? Does your friend make the child feel wanted or like an inconvenience? Is the child afraid to lose your friend? She should really spend some one-on-one time with this little guy with the potty issues aside and give him love...it does conquer all, right? I will keep them in my prayers.