Martin, if you want to believe that a picture of an ambulance zooming down a street is street photography, be my guest. Street photography is photography that shows interesting and often ambiguous interrelationships between people and other people and between people and their environment. This picture doesn't show either thing.
Ah, but it
so does.
It is not just "an ambulance zooming down a street." It has something extra than makes the shot: the cross reflection. It also contains the exact moment the ambulance touches the reflection, merging for a split second with it symbolically and symbiotically.
It
does contain people and their interaction with the environment.
Just like street photography doesn't need to happen only on the street, people street photography doesn't need to obviously show people, if their presence is palpable. There are people in that ambulance, one of which is in critical condition, and, like most people, turning to God for help, even if metaphorically so. And here we have a cross* (pardon the pun) between two crosses: one symbolizing modern medicine, on a modern vehicle, and the other ancient, symbolizing the eternal belief in divine intervention and ultimate salvation.
This image is so much more about human presence than, for instance, two old guys shooting the breeze, or someone sitting in a cafe window, or colorful socks.
* Or, as OnlyNorth rightly suggests, a cooperation