I haven’t lived in MI for about a decade, but I’m going to venture a guess (admittedly without reading the full article) that these people are more than likely residing in and around Ann Arbor. Romney would be about as conservative as Ann Arbor is capable of. The west side of the state as a whole is much more conservative especially Grand Haven and Holland areas.
Willow Run is the east side of Ypsi. It's heavily union and democrat.
Brighton is one of the most conservative areas in southeast Michigan but George Romney was buried there.
Birmingham is next door to Romney's old hometown. They may well known some of the Romney family.
Plymouth is a largely establishment republican area.