I don't think that there's any "great" solution for interaction between cyclists and peds on a MUP. I will say that, in my personal observation (as a runner and cyclist), that the absolute worst people on a MUP are those out for a leisurely stroll. They have every right to use the path, but they are generally the ones that will walk up the wrong side of the path, or right down the middle with a pet on a leash/ children, or a whole group taking up the entire width of a path. No matter what you call out, they are so ignorant/oblivious to the rest of the world that they present a danger to anybody on a bike, and major annoyance to runners. The annoyance/danger is multiplied when they are plugged in to their mp3 players and have them blaringly loud.

Just last night, I was jogging on a MUP and the weather was quite nice so the "strollers" were out in force. The path I was on is ~8 feet wide and as I'm approaching a couple of older women (from the front, they could easily see me, and my day-glo shirt) one of the older ladies actually stepped IN MY WAY and was doing a weird fake jogging pantomime. I'm sure that she thought she was being funny, or friendly, or something, but she caused me to have to slam on my brakes. Totally unaware that I could've twisted an ankle/knee, or not been able to halt as fast as I did and I would've bowled her over.
All the paths around me are like that. It's kind of getting to the point that I prefer to use the paths when it's raining, or at some ungodly hour (though that is not a great choice, because technically the paths are closed from dusk to dawn, also there are other safety issues) so I can avoid the casual users.

Obviously, that article doesn't/can't give all of the details, so I hope the cyclist was acting properly and this was just an unavoidable accident.