I was shopping on line at a major supermarket and noticed items from major brands that the ingredients list lists mechanically separated pork and chicken. I don't know about the pork or chicken but as for the beef I found the following link.
My knowledge MSM Beef was banned in 2004 but had been used since at least the 80s before that. I originally heard about this from my dad who was and is still a butcher manager.
I just texted him and he said that MSM Beef is still prohibited for human consumption because of mad cow disease but mechanically separated Pork is legal and can be used when the package says so. He was not sure about chicken but if it's not banned then they probably do put it in products. he says he likes that they "use as much of the animal as possible but yes , its kinda gross."