For me, it is the details . . .
The curve of the front nose corners, the the "box" around the upper and lower grills (though, it has a bit of an extended jaw), the shape of the headlights (except their turn signal is our main light and their headlight is our "brights" and turn signal).
The similarity is striking.
Though the UPS truck has a higher roof above the windshield line.
I gave gotten a number of "1/55" scale diecast UPS trucks that I am painting like my xB.
(The Blackberry Crush looks even more like it. Though in some lights it looks more purple.)