Who was getting the royal treatment in Newton?

Jo comes out of the Chestnut Hill Mall on Saturday evening to find at least one police cruiser with lights flashing at each intersection on Comm. Ave. between Hammond Pond Parkway and Auburndale. She wonders who the somebody was who merited such attention:

... A couple of miles later where Comm Ave. insterstects with Auburn St. suddenly we saw 3 or 4 police bikes escorting about 4 large buses speeding Eastbound on Comm Ave. The buses all looked rather nondescript but they did have blacked out windows. ...